An AGN Sample with High X-ray-to-optical Flux Ratio from RASS II.Optical Emission Line Prop

合集下载

光的衍射英文作文

光的衍射英文作文Diffraction of LightLight is a fundamental aspect of our universe, and its behavior has been a subject of fascination for scientists and philosophers alike throughout history. One of the most intriguing phenomena associated with light is the process of diffraction, which has profound implications for our understanding of the nature of light and its interaction with the physical world.Diffraction is the bending or spreading of waves as they encounter an obstacle or an aperture. This phenomenon is not limited to light but can be observed in various types of waves, including sound, water, and even certain types of subatomic particles. When light encounters an obstacle or an aperture, it bends around the edges, creating a pattern of light and dark regions that is distinctly different from what would be expected if the light simply traveled in a straight line.The study of light diffraction has led to numerous important discoveries and technological advancements. One of the most significant applications of diffraction is in the field of optics, where itis used to design and optimize various optical devices, such as telescopes, microscopes, and lasers.In a telescope, for example, the objective lens or mirror is designed to collect and focus the light from distant objects, allowing us to observe them in greater detail. However, the size of the objective lens or mirror also determines the resolution of the telescope, which is the ability to distinguish between two closely spaced objects. This is where diffraction comes into play. As the light passes through the objective, it is diffracted, creating a pattern of light and dark regions known as the Airy disk. The size of the Airy disk is inversely proportional to the diameter of the objective, meaning that a larger objective will produce a smaller Airy disk and, consequently, a higher resolution.Similarly, in the case of microscopes, diffraction plays a crucial role in determining the resolution of the instrument. The wavelength of the light used in the microscope, as well as the numerical aperture of the objective lens, are important factors that determine the diffraction pattern and, ultimately, the resolution of the microscope.Diffraction also has important applications in the field of spectroscopy, where it is used to separate the different wavelengths of light emitted by a source. This is achieved by passing the light through a diffraction grating, which is a series of evenly spaced slitsor grooves that act as a dispersive element, separating the light into its constituent wavelengths.Another fascinating application of diffraction is in the field of holography, where it is used to create three-dimensional images of objects. In a holographic system, a coherent light source, such as a laser, is split into two beams: a reference beam and an object beam. The object beam is reflected off the object being imaged, and the resulting diffraction pattern is recorded on a photographic plate or a digital sensor. When the recorded hologram is illuminated by the reference beam, the diffraction pattern is reconstructed, creating a three-dimensional image of the original object.Diffraction also plays a crucial role in the study of the wave-particle duality of light. According to the principles of quantum mechanics, light can exhibit both wave-like and particle-like properties, depending on the experimental conditions. The diffraction of light is a clear demonstration of its wave-like behavior, as it cannot be explained solely by the particle model of light.In conclusion, the phenomenon of light diffraction is a fundamental aspect of our understanding of the physical world. It has led to numerous important discoveries and technological advancements, and continues to be a subject of intense study and research in various fields of science and engineering. As we continue to explorethe intricacies of light and its behavior, the study of diffraction will undoubtedly remain a crucial part of our quest to understand the nature of the universe.。

《understanding optics with python》 -回复

《understanding optics with python》-回复《Understanding Optics with Python》Optics, the branch of physics dealing with the properties and behavior of light, plays a crucial role in various fields, including physics, engineering, and even everyday life. In this article, we will explore the fascinating world of optics using the programming language Python. We will take a step-by-step approach to delve into the fundamental concepts and principles of optics and demonstrate how Python can be leveraged to solve optical problems.Introduction to Optics:Optics is the science of light and its interaction with matter. It encompasses the study of reflection, refraction, diffraction, interference, and the production and detection of light. Understanding optics is essential in various applications, such as designing lenses, cameras, telescopes, and lasers.Using Python for Optical Calculations:Python is a versatile programming language that is widely used in scientific research and engineering. Its extensive libraries andintuitive syntax make it a powerful tool for performing optical calculations and simulations. Let's take a look at how Python can be leveraged in optics.1. Calculating Refraction using Snell's Law:One of the fundamental principles in optics is Snell's Law, which describes the behavior of light when it passes from one medium to another. We can write a Python code snippet to calculate the angle of refraction using Snell's Law for a given incident angle and refractive indices of the media involved.2. Modeling Lens Systems:Lenses are crucial optical devices used in various applications, from eyeglasses to cameras. Python's numerical and plotting libraries allow us to model and simulate lens systems. We can create a simple program that models the behavior of different types of lenses and their effect on light rays.3. Simulation of Interference Patterns:Interference is a fascinating phenomenon that occurs when two or more waves superpose. Python's numerical libraries enable us to simulate and visualize interference patterns. We can write a codethat generates interference patterns by combining waves of different frequencies and phases.4. Analyzing Diffraction Patterns:Diffraction refers to the bending of light around obstacles or through narrow openings. Python can be used to analyze and visualize the diffraction patterns produced by various apertures. By employing the Fourier transform, we can calculate and plot diffraction patterns for different scenarios.5. Designing Optical Filters:Optical filters are essential in many applications, such as photography, spectroscopy, and signal processing. Python can be utilized to design and optimize optical filters by manipulating the spectral transmission or reflection properties of materials. We can create a program that designs bandpass filters based on given specifications.6. Ray Tracing for Optical Systems:Ray tracing is a powerful technique used in optics to simulate the path of light rays through complex systems. Python's libraries can be employed to create a ray tracing program that models thebehavior of light in optical systems, including reflection, refraction, and multiple interactions with lenses and mirrors.Conclusion:Python provides a comprehensive set of tools and libraries for understanding and solving problems in optics. From the basics of refraction and lens systems to the complex phenomena of interference and diffraction, Python enables us to simulate and analyze optical systems with ease. By leveraging the power of Python, students, researchers, and professionals can enhance their understanding and explore the fascinating world of optics. So, pick up Python and embark on a journey to explore the wonders of optics!。

Unconventional AGN in hard X-ray surveys

arXiv:as tr o-ph/21136v114Nov22Astron.Nachr./AN 32X (200X)X,XXX–XXXCorrespondence to :comastri@anastasia.bo.astro.it⋆ A.Baldi,P.Ciliegi,F.Cocchia,F.Fiore, Franca,R.Maiolino,G.Matt,S.Molendi,G.C.Perola,C.Vignali veys fall within −1<log (f X /f opt )<1.Extensive optical follow–up observations of hard X–ray sources discovered by deep and medium deep Chandra and XMM–Newton surveys conﬁrm this trend to fainter X–ray ﬂuxes and,at the same time,show evidence of a relatively large number of sources which deviate from log (f X /f opt )=0±1(Fig.1).For the purposes of the present paper it is convenient to divide the “outliers”in two groups.The ﬁrst includes sources that are X–ray weak for their R band magnitudes (log f X /f opt ≃–1);the second,sources that are optically faint (sometimes below the limits of deep optical images)and relatively X–ray bright (log f X /f opt >1).In the following we refer to both classes of sources as unconventional AGN.The identiﬁcation breakdown of the sources in the ﬁrst group is a mixed bag including emission line galaxies and ap-parently normal galaxies (see Alexander et al.this volume).A sizeable fraction of the latters,named XBONG (X–ray Bright Optically Normal Galaxies;Comastri et al.2002b),are par-ticulary intriguing being characterized by an absorption dom-inated optical spectrum and AGN–like hard X–ray luminosi-ties (L 2−10≃1042−43erg s −1).They are found at moder-ately low redshift,(z <1;Hornschemeier et al.2001,Barger et al.2002).The average value of their log f X /f opt distribu-tion is around –1with a large dispersion (Fig.3).An attempt to deeply investigate their nature through a multiwavelength approach suggests that the putative AGN responsible for the hard X–ray emission is completely hidden at longer wave-lengths (Comastri et al.2002a).The sources characterized by high values of f X /f opt are even less understood.The spectroscopic identiﬁcation of these objects is already challenging the capabilities of 8–10m optical telescopes calling for the next generation of224Astron.Nachr./AN XXX(200X)Xastri:Unconventional AGN225226Astron.Nachr./AN XXX(200X)X。

Growth and applications of group III-nitrides

J.Phys.D:Appl.Phys.31(1998)2653–2710.Printed in the UK PII:S0022-3727(98)68952-XREVIEW ARTICLEGrowth and applications ofGroup III-nitridesO AmbacherWalter Schottky Institute,Technical University Munich,Am Coulombwall,D-85748Garching,GermanyReceived18February1997,inﬁnal form15June1998Abstract.Recent research results pertaining to InN,GaN and AlN are reviewed,focusing on the different growth techniques of Group III-nitride crystals andepitaxialﬁlms,heterostructures and devices.The chemical and thermal stability ofepitaxial nitrideﬁlms is discussed in relation to the problems of depositionprocesses and the advantages for applications in high-power and high-temperaturedevices.The development of growth methods like metalorganic chemical vapourdeposition and plasma-induced molecular beam epitaxy has resulted in remarkableimprovements in the structural,optical and electrical properties.New developmentsin precursor chemistry,plasma-based nitrogen sources,substrates,the growth ofnucleation layers and selective growth are covered.Deposition conditions andmethods used to grow alloys for optical bandgap and lattice engineering areintroduced.The review is concluded with a description of recent Group III-nitridesemiconductor devices such as bright blue and white light-emitting diodes,theﬁrstblue-emitting laser,high-power transistors,and a discussion of further applicationsin surface acoustic wave devices and sensors.1.IntroductionGroup III-nitrides have been considered a promising system for semiconductor devices applications since1970, especially for the development of blue-and UV-light-emitting diodes.The III–V nitrides,aluminium nitride (AlN),gallium nitride(GaN)and indium nitride(InN), are candidate materials for optoelectrical applications at such photon energies,because they form a continuous alloy system(InGaN,InAlN,and AlGaN)whose direct optical bandgaps for the hexagonal wurtzite phase range from 1.9eV forα-InN and 3.4eV forα-GaN to 6.2eV forα-AlN.The cubic modiﬁcations have bandgaps in the range from 1.7eV forβ-InN and 3.2eV for β-GaN to 4.9eV forβ-AlN(ﬁgures1and2)[1–6]. Other advantageous properties include high mechanical and thermal stability,large piezoelectric constants and the possibility of passivation by forming thin layers of Ga2O3 or Al2O3with bandgaps of approximately 4.2eV and 9eV.The spontaneous and piezoelectric polarization(in the wurtzite materials)and the high electron drift velocities (2×105m s−1[7])of GaN can be used to fabricate high-power transistors based on AlGaN/GaN heterostructures. In addition,AlN is an important material with a variety of applications such as passive barrier layers,high-frequency acoustic wave devices,high-temperature windows,and dielectric optical enhancement layers in magneto-optic multilayer structures[8,9].Very informative reviews of the growth techniques and structural,optical and electrical properties of Group III-nitrides and their alloys have been presented by Strite et al[10,11].A good overview of applications of Group III-nitride based heterostructures for UV emitters and high-temperature,high-power electronic devices is provided in[12]and[13].This review focuses on the development of the different growth techniques successfully applied to the deposition of Group III-nitride epitaxial ﬁlms and heterostructures,such as chemical transport and metalorganic chemical vapour deposition(MOCVD), sputtering and molecular beam epitaxy(MBE).The quality of state-of-the-art material and its application for optical and electronic devices are discussed in detail in order to point out possible limitations,promising developments and future trends.Theﬁrst systematic effort to grow InN,GaN and AlN by chemical vapour deposition or sputtering processes took place in the1970s in order to characterize the optical and structural properties of thinﬁlms.At that time, neither metalorganic precursors containing In or Al with electronic grade purity,plasma sources for nitrogen radicals compatible with MBE systems,nor substrate material with reasonably good thermal and lattice matches to the nitrides were available.The InN and GaN material had large concentrations of free electrons,presumed to result from oxygen impurities and intrinsic defects,and the structural quality of the AlNﬁlms was not good enough for optical0022-3727/98/202653+58$19.50c 1998IOP Publishing Ltd2653OAmbacherFigure 1.Bandgap and bowing parameters of hexagonal (α-phase)and cubic (β-phase)InN,GaN,AlN and their alloys versus lattice constant a 0[1–6].or electronic applications.Primarily,the development of MOCVD and plasma-induced molecular beam epitaxy (PIMBE)over the last eight years has led to a number of recent advances and important improvements in structural properties.2.Crystal structure,polarity and polarization of InN,GaN and AlNIn contrast to cubic III–V semiconductors like GaAs and InP with the zincblende structure,the thermodynamically stable phase of InN,GaN and AlN,is the hexagonal wurtzite structure (α-phase).Beside the α-phase,a metastable β-phase with zincblende structure exists and a cubic high-pressure modiﬁcation with NiAs structure was observed for pressures above 25kbar in the case of AlN [14].Because the α-and β-phases of Group III-nitrides only differ in the stacking sequence of nitrogen and metal atoms (polytypes),the coexistence of hexagonal and cubic phases is possible in epitaxial layers,for example due to stacking faults.The hexagonal crystal structure of Group III-nitrides can be described by the edge length a 0of the basal hexagon,the height c 0of the hexagonal prism and an internal parameter u deﬁned as the anion–cation bond length along the (0001)axis.Because of the differentcations and ionic radii (Al 3+:0.39˚A,Ga 3+:0.47˚A,In 3+:0.79˚A[15]),InN,GaN and AlN have different lattice constants,bandgaps and binding energies as shown in table 1[16,17].Both wurtzite and zincblende structures have polar axes (lack of inversion symmetry).In particular,the bondsinFigure 2.Experimental results of bandgaps of hexagonal Group III-nitrides versus lattice constant c 0at room temperature [1–6].Table ttice constants,bandgaps and binding energies of hexagonal InN,GaN and AlN.Wurtzite,300K AlN GaN InN a 0(˚A)b 3.112 3.189 3.54c 0(˚A)b 4.982 5.185 5.705c 0/a 0(exp.)b 1.6010 1.6259 1.6116c 0/a 0(calc.)a 1.6190 1.6336 1.6270u 0a0.3800.3760.377a Bohr (˚A)a 5.814 6.04 6.66E B (M–N)c (eV)b2.882.201.98a From [16].b From [17].cM =In,Ga or Al,N =nitride.the 0001 direction for wurtzite and 111 direction for zincblende are all faced by nitrogen in the same direction and by the cation in the opposite direction.Both bulk and surface properties can depend signiﬁcantly on whether the surface is faced by nitrogen or metal atoms [18,19].The most common growth direction of hexagonal GaN is normal to the {0001}basal plane,where the atoms are arranged in bilayers consisting of two closely spaced hexagonal layers,one with cations and the other with anions,so that the bilayers have polar faces.Thus,in the case of GaN a basal surface should be either Ga-or N-faced.By Ga-faced we mean Ga on the top position of the {0001}bilayer,corresponding to [0001]polarity (ﬁgure 3).Ga-faced does not mean Ga-terminated;termination should only be used2654Growth and applications of GroupIII-nitridesFigure3.Different polarities(Ga-and N-faced)of wurtzite GaN.to describe a surface property.A Ga-face surface mightbe N-terminated if it is covered with nitrogen atoms,butwithoutﬂipping the crystal it will never be N-faced.Itis,however,important to note that the(0001)and(000¯1) surfaces of GaN are inequivalent(by convention,the[0001]direction is given by a vector pointing from a Ga atom toa nearest-neighbour N atom).It has been reported that high-quality epitaxial GaNﬁlms deposited by MOCVD on c-plane sapphire substratesgrow in the(0001)direction with Ga-faced surfaces,whileMBE growth commonly occurs in the(000¯1)direction, yielding an N-facedﬁlm[20–22].Polar faces are known to have very marked effectson growth in binary cubic semiconductors.For example,growth along the Ga-faced{111}direction of GaAs isknown to be slow and has the tendency to produce planarsurfaces,whereas growth of the As-face is fast and rough[23].Similarly,Ponce et al found that the smooth sideof bulk single crystal platelets corresponds to the Ga-face(0001)whereas the N-face(000¯1)is much rougher[20].In the following we will discuss the inﬂuence ofspontaneous and piezoelectric polarization on the physicalproperties of Group III-nitrides.This class of polarization-related properties is obviously important for devices(section9)because the electricﬁelds inﬂuence the shapeof the band edges and the carrier distribution insidenitride-based heterostructures.Therefore spontaneousand piezoelectric polarization can inﬂuence the radiativerecombination in light-emitting devices as well as theelectrical properties of the transistor structures discussedin detail later.Wurtzite is the structure with highest symmetrycompatible with the existence of spontaneous polarization[16,24,25]and the piezoelectric tensor of wurtzite hasthree independent nonvanishing components.Therefore,polarization in these material systems will have both aspontaneous and a piezoelectric component.Becauseof the sensitive dependence of spontaneous polarizationon the structural parameters,there are some quantitativedifferences in polarization of the three nitrides studied here.The increasing nonideality of the crystal structure going Table2.Spontaneous polarization,piezoelectric and dielectric constants of AlN,GaN and InN.Wurtzite AlN GaN InNP SP(C m−2)−0.081−0.029−0.032e33(C m−2) 1.46a0.73a0.97a1.55b1c0.65d0.44ee31(C m−2)−0.60a−0.49a−0.57a−0.58b−0.36c−0.33d−0.22ee15(C m−2)−0.48b−0.3c−0.33d−0.22eε119.0b9.5fε3310.7b10.4fa From[16].b From[26].c From[27].d From[28].e From[29].f From[30].from GaN to InN to AlN(u0increases and c0/a0decreases (table1)),corresponds to an increase in spontaneous polarization.In the absence of external electricﬁelds,the total macroscopic polarization P of a solid is the sum of the spontaneous polarization P SP in the equilibrium lattice and the strain-induced or piezoelectric polarization P P E.Here we consider polarizations along the(0001)axis, because this is the direction along which standard bulk materials,epitaxialﬁlms and heterostructures are grown. Spontaneous polarization along the c-axis is P SP=P SP z (the direction of spontaneous polarization is determined by the polarity;the direction of the piezoelectric polarization depends on the polarity and whether the material is under tensile or compressive stress)and piezoelectric polarization can be calculated by using the piezoelectric coefﬁcients e33 and e13(table2)asP P E=e33εz+e31(εx+εy)(1) where a0and c0are the equilibrium values of the lattice parameters,εz=(c−c0)/c0is the strain along the c-axis, and the in-plane strainεx=εy=(a−a0)/a0is assumed to be isotropic.The third independent component of the piezoelectric tensor,e15,is related to the polarization induced by shear strain and will not be discussed.To give an example of the possible inﬂuence of polarization on the physical properties of nitride-based heterostructures,we calculate the electricﬁeld caused by polarization inside a Ga-faced Al x Ga1−x N/GaN/Al x Ga1−x N quantum well.We assume that the GaN is grown pseudomorphically on the AlGaN(a(GaN)=a(AlGaN))2655O AmbacherTable3.Experimental and calculated values of the piezoelectric constants and bulk modulus for wurtzite and zincblende Group III-nitrides.AlN GaN InNGPawurtzite exp.a calc.b exp.c calc.b exp.d calc.bC11345396374367190223C12125137106135104115C131201087010312192C33395373379405182224C44118116101951048B201207180202139141zincblende calc.e calc.b calc.e calc.b calc.e calc.bC11304304296293184187C12152160154159116125C4419919320615517786a From[31].b From[32].c From[33].d From[34].e From[35].and that screening effects due to free carriers and surface states can be neglected.The lattice constants a and c of the GaN layer are decreased and increased respectively,due to the biaxial compressive stress which becomes larger with increasing Al content of the AlGaNﬁlm.The relation between the lattice constants of the hexagonal GaN is given byc−c0 c0=−2C13C33a−a0a0(2)where C13and C33are elastic constants(table3). Using equations(1)and(2)the amount of piezoelectric polarization in the direction of the c-axis can be determined byP P E=2a−a0a0e31−e33C13C33.(3)The strain of the pseudomorphically grown GaN can be calculated using Vegard’s law(linear interpolation of the lattice constants of relaxed Al x Ga1−x N from the values for GaN and AlN:a(x)=(−0.077x+3.189)˚A(table1)), leading toP P E(GaN)=0.0163x C m−2(4) and a total polarization ofP(GaN)=P SP(GaN)+P P E(GaN)=(−0.029+0.0163x)C m−2.(5) The polarization generates an electricﬁeld E(GaN)inside the GaN layer:E(GaN)=−P(GaN)ε(GaN)ε0=(3.6×106−2.1×106x)V cm−1(6) whereε(GaN)(table2)andε0are the dielectric constants of GaN andvacuum.Figure4.Polarization(spontaneous,piezoelectric and total polarization)of a relaxed Al x Ga1−x N and a pseudomorphic on top of Al x Ga1−x N grown GaN layer versus Al content x. The interface chargeσis caused by the different total polarizations of the GaN and the AlGaNﬁlm.The AlGaN is assumed free of strain and therefore the piezoelectric polarization equals zero.The total polarization of the AlGaN can be described by a linear approximation between the spontaneous polarization of GaN and AlN:P(AlGaN)=P SP(AlGaN)=(−0.029−0.052x)C m−2.(7)A charge density at the GaN/AlGaN interfaces,σ(GaN/ AlGaN),is caused by the different polarizations of GaN and AlGaN:±σ(GaN/AlGaN)=P(GaN)−P(AlGaN)=±0.068x C m−2.(8) The spontaneous polarization,piezoelectric polarization and interface charge density of GaN embedded in two Al0.15Ga0.85N layers are determined to be−0.029,0.0025 and±0.0025C m−2respectively.(For AlGaN/GaN/AlGaN heterostructures with different Al content x,seeﬁgure4.) The electricﬁeld caused by polarization effects can reach a strength of3×106V cm−1.The modiﬁcation of the band edges due to spontaneous polarization and piezoelectricﬁelds inside the GaN layer can have a signiﬁcant inﬂuence on the optical properties (ﬁgure5).Due to the Stark and Franz–Keldysh effects, the effective bandgap of GaN will be red-shifted and the recombination probability of electron hole pairs will be decreased because of the spatial separation of electrons and holes[36,37].These physical effects thus change the energy of the electroluminescence out of GaN or InGaN2656Growth and applications of GroupIII-nitridesFigure5.Conduction and valence band edges of a pseudomorphic grown AlGaN/GaN/AlGaN(x=0.15)andGaN/InGaN/GaN(x=0.06)heterostructure.The arrows indicate schematically the radiative recombination of an electron and a hole,which is red-shifted in comparison to the bandgap energy due to the Stark effect.quantum wells and the recombination rates of carriers inside a Group III-nitride based laser structure(section9.5).The strong electricﬁelds can also enhance electron or hole accumulation at AlGaN/GaN interfaces(ﬁgure5).This effect can be used in heterostructureﬁeld effect transistors, as discussed later in section9.3.At which interface (lower or upper)of a AlGaN/GaN/AlGaN heterostructure electrons or holes are conﬁned depends on the polarity of the material.In respect of polarization effects,the Group III-nitrides exhibit unusual properties.The piezoelectric constants have the same sign as in II–VI compounds,and opposite to those of III–V compounds.The absolute values of the piezoelectric constants are up to ten times larger than in conventional III–V and II–VI compounds.In particular the constants e33and e31of AlN are larger than those of ZnO and BeO[38],and are therefore the largest known so far among the tetrahedrally bonded semiconductors.The spontaneous polarization(the polarization at zero strain) is also very large in the nitrides.That of AlN is only about three toﬁve times smaller than in typical ferroelectric perovskites[39].For these reasons,the spontaneous and piezoelectric polarization of hexagonal Group III-nitrides can have a much larger inﬂuence on the electrical and optical properties of devices than in other III–V compounds. Finally it should be mentioned that free carriers with a concentration above1018cm−3,charged defects or compensation of surface charges by adsorbates can reduce the polarization-induced electricﬁelds and have to be considered in a detailed analysis of polarization-related effects.3.Thermal properties and stabilityThe primary methods of obtaining crystal material rely on growing epitaxial layers on different substrates at high temperatures.Unfortunately,the different coefﬁcients of thermal expansion between substrate and nitride introduce residual stress upon cooling.These induced stresses can cause additional structural defects and piezoelectricﬁelds and will inﬂuence the optical and electrical properties of ﬁlms and devices.The determination of thermal expansivity is not only related to other thermal properties(thermal conductivity, speciﬁc heat)but can also yield parameters pertinent to2657OAmbacherFigure ttice constant and c /a ratio versus temperature.other basic properties,like the temperature dependence of the band gap [2].The value of the thermal expansion coefﬁcient depends on many parameters,such as defect concentration,free carriers,and strains,and the published values are somewhat scattered.The thermal expansivities perpendicular and parallel to the c -axis in hexagonal material are usually different.The lattice parameters and the thermal expansion coefﬁcient have been measured to intermediate temperatures for AlN,GaN and once for InN [30,40–46].The increase of the lattice constant a and the thermal expansion coefﬁcients of hexagonal InN,GaN and AlN with increasing temperature measured by different groups are shown for comparison in ﬁgures 6and 7.As the lattice constants a and c increase,the c/a ratio of the lattice constants becomes smaller with increasing temperature.The experimental data of the lattice constants and thermal expansion coefﬁcients for AlN and GaN are in good agreement with the theoretical calculations of Wang and Reeber (ﬁgure 7)[47].The calculated thermal expansion coefﬁcients of AlN,GaN and InN at 100K are 1.3×10−8K −1,1.2×10−6K −1and 2.4×10−6K −1for a 0and −5×10−8K −1,1.1×10−6K −1and 2.8×10−6K −1for c 0.At 600K,these values become 5.3×10−6K −1,5×10−6K −1and 5.7×10−6K −1for a 0and 4.4×10−6K −1,4.4×10−6K −1and 3.7×10−6K −1for c 0.Below 100K the thermal expansion coefﬁcient of AlN was calculated to be negative.Above 600K up to the decomposition temperature (discussed below),the thermal expansion coefﬁcients gradually increase by up to 25%.The lattice constants,binding energy and decomposi-tion temperature of Group III-nitrides have important con-sequences for the thermal stability of nitride-baseddevices.Figure 7.Thermal expansion coefﬁcients parallel (α(c ))and perpendicular (α(a ))to the c -axis versus temperature.The relatively large range of uncertainty and the limited number of experimental data concerning nitrogen diffusion,the temperature dependence of the nitrogen ﬂux from a ni-tride crystal surface and the nitrogen pressures necessary to stabilize a GaN melt are due in part to the very high melt-ing points T M and N 2equilibrium pressures of the Group III-nitrides.Recently,the thermal stability of InN was investigated at N 2pressures extending up to 18.5kbar [48].It was shown by differential thermal analysis that,over the whole investigated pressure range (0.1–18.5kbar),rapid decomposition of InN occurs above (710±10)◦C.Trainor and Rose [49]observed dissociation of thin InN ﬁlms at 500◦C and 1bar N 2.Guo and Kato [50]observed a change of the reﬂective high-energy electron diffraction (RHEED)pattern of InN single crystal ﬁlms when the temperature was raised above 550◦C.They concluded that the crystals decomposed to In and N 2above that temperature.MacChesney et al observed the equilibrium partial pressure of N 2over InN to be 1bar at 800K,increasing exponentially with 1/T to 105bar at 1100K [51](ﬁgure 8).The ﬁrst study of the thermal stability of GaN was made by Johnson et al [52].More recently Sime and Margrave [53]investigated the evaporation of GaN and Ga metal in the temperature range 900to 1150◦C at 1atm pressure of N 2,NH 3and H 2,while studying the formation and decomposition equilibria.They determined the heat of evaporation and proposed the existence of [GaN]x polymers in the gas phase.Thurmond and Logan [54]chemically measured the partial pressure ratios which2658Growth and applications of GroupIII-nitridesFigure8.Equilibrium N2pressure over the MN(s)+M(l) systems(M=In,Ga or Al),and melting points T M from high-pressure experiments and theoretical calculations [48–60].exist in a(H2+NH3)gas mixture streaming over Ga and GaN.They determined the equilibria both in the case of formation and decomposition of GaN.Lorenz and Binkowski[55]observed the decomposition at given temperatures by measuring the time dependence of the increase in N2pressure.An extensive study on the thermal stability of GaN at high temperatures and pressures up to60kbar has been performed by Karpinsky et al[56], using a gas pressure technique and a tungsten carbide anvil cell.In the high-pressure range,the p(1/T)curve strongly deviates from the linear dependence proposed by Thurmond and Logan(ﬁgure8),but there is good agreement in the Gibbs free enthalpy with G0=(32.43T−3.77×104)cal/mol for GaN synthesis.The value of enthalpy H0of−37.7kcal/mol is in good agreement with the value estimated by Madar et al[57].Resistively heated graphiteﬁlaments were used by Class[58]to evaluate the melting behaviour and temperature of AlN.The melting of AlN was observed at 2750–2850◦C,at nitrogen pressures of100and200bar. Slack and McNelly[59]calculated N2pressures over AlN in equilibrium with liquid Al to be1,10and100bar at 2563◦C,2815◦C and3117◦C respectively.The melting temperatures for different nitrides were evaluated by Van Vechten[60]with the use of a semi-empirical theory for electronegativity,concluding that the melting point of AlN is close to3487K.Figure8summarizes the results of the theoretical calculations and experiments described above, including the meltingtemperatures.Figure9.The partial pressure of mass28amu(N+2,CO+, C2H+4)versus effusion or decomposition temperature T E. The decomposition of InN,GaN and AlN is observed above 630◦C,850◦C and1040◦C respectively[61].To quantitatively determine and compare the thermal stability of thinﬁlms,the desorption and decomposition of polycrystalline InN deposited at550◦C,and epitaxial GaN and AlN grown at950◦C and1050◦C were measured by heating the samples in vacuum and recording the partial pressure of relevant gases using a quadrupole mass spectrometer[61].For a known heating routine,the desorption spectra can be analysed toﬁnd the binding energies of various desorbed species as well as the thermal stability of the sample[62].Figure9shows the partialpressure of mass28amu(N+2,CO+,C2H+4)versus effusion or decomposition temperature T E.The nitrogen partial pressure increases exponentially above T E=630◦C, 850◦C and1040◦C for InN,GaN and AlN respectively, illustrating that the decomposition temperature in vacuum is much lower than the melting point.To determine the effective decomposition activation energy more precisely, the nitrogenﬂux was calculated from the measured nitrogen pressure.The rate of nitrogen evolution (N)is equal to the rate of decomposition,and the slope of ln[ (N)] versus1/T(ﬁgure10)gives the effective activation energy of the decomposition in vacuum E MN.The decomposition rate equals the desorption of one monolayer every second( (N)=1.5×1015cm−2s−1)at795,970 and1050◦C,and the activation energy of the thermally induced decomposition is determined to be E MN=3.5eV (336kJ mol−1), 3.9eV(379kJ mol−1)and 4.3eV (414kJ mol−1)for InN,GaN and AlN respectively(table4). This indicates temperature limits for high-temperature or high-power devices.2659OAmbacherFigure 10.Nitrogen ﬂux or desorption rate for InN,GaN and AlN in the temperature range of decomposition.The rate of N evolution is equal to the rate of decomposition and the slope of ln[ (N)]versus 1/T gives the effective activation energy E MN of the decomposition in vacuum [61].Table 4.Density ρ,melting point T M ,decomposition temperature T E and activation energy E MN of thedecomposition of InN,GaN and AlN (p <10−6mbar).ρaT M a T E b E MN b(g cm −3)(K)(◦C)(kJ mol −1)AlN 3.2934871040414GaN 6.072791850379InN6.812146630336a From [17].bFrom [61].In connection with the thermal stability of hexagonal nitrides,the thermally activated nitrogen self-diffusion should be mentioned.Nitrogen diffusion is a fundamental transport process in Group III-nitrides.In general,self-diffusion processes in wide-bandgap semiconductors or insulators are more complex than in metals [63].This is due to the large variety of native defects,different possible charge states of defects,and to the much larger effects of small concentrations of defects on the Fermi level position [64].Diffusion processes also play an important role in device fabrication and the thermal stability of high-power devices [65].Diffusion of dopants is utilized to engineer p–n junctions and transistor structures [66].In other cases,diffusion can be destructive to delicate structures due to the transport of dopants from thin layers into the adjacent layers or thesubstrate.Figure 11.Arrhenius plot of the measured nitrogen self-diffusion coefﬁcient in hexagonal GaN,obtained at temperatures between 770and 970◦C.The diffusion coefﬁcients were calculated from the concentration depth proﬁles determined from SIMS signals of 14N (opensquares),15N (open circles),14N 2(full squares)and 15N 2(full circles).The line represents a least-squares ﬁt to the measured data.In III–V compounds,diffusion measurements are difﬁcult to perform because of the high partial vapour pressure of the Group V elements and the dependence of native defect species and concentrations on stoichiometry.Goldstein [67]and Palfrey et al [68]diffused radioactive 72Ga into bulk GaAs to study Ga self-diffusion.The measurement of the depth proﬁle of 72Ga was realized by mechanical sectioning and determination of the radioactivity.Within the temperature range investigated,the authors reported activation enthalpies varying between 2.6and 5.6eV.Wang et al [69]grew and studied an isotopically tagged 69GaAs/71GaAs heterostructure.Upon heating between 800and 1225◦C under an As-rich condition,the Ga diffusion coefﬁcient D was determined by secondary ion mass spectrometry (SIMS)to be D(Ga )=(43±25)cm 2s −1exp[(−4.24±0.06)eV k −1BT −1]over six orders of magnitude in D .In analogy to that experiment,nitrogen self-diffusion was studied by using Ga 14N/Ga 15N/Ga 14N (500/500/500nm)isotopic heterostructures grown on c -plane sapphire by PIMBE [70].Concentration proﬁles of nitrogen isotopes after annealing were measured using SIMS.The activation enthalpy and entropy of nitrogen self-diffusion were obtained by analysing the diffusion length measured for annealing temperatures between 7702660。

应用光学(appliedoptics)中英对照复习资料第1章

应用光学(applied optics) 中英对照复习资料第1章1、光学研究分为两类:物理光学和几何光学.There are two aspects of people’s study of light: physical optics and geometrical optics. 2、光实际是电磁波.light is an electromagnetic wave3、光具有波粒2象性: a kind of matter with wave-particle duality, namely it has the characteristics of both the waves and the corpuscles.4、可见光visible light波长范围:400nm~760nm5、光速、频率、波长关系the relation among the speed of light, the frequency and wavelength ofcand electromagnetic wave.：,, ,6、波面wavefront是所有光线的垂直perpendicular surface曲面。

或光线垂直于波面：rays are perpendicular to wavefront.典型波面：同心光束concentric beam波面为球面sphere(spherical surface)；像散光束astigmatic beam波面为非球面aspheric shape(aspheric surface)；平行光束parallel beam波面为平面plane(plain surface)。

7、几何光学基本定律。

Basic laws of geometrical optics1)直线传播定律：光线在均匀透明介质中按直线传播。

The law of rectilinear propagation: rays propagate along straight lines in a homogeneous and transparent medium.2)反射定律：the law of reflection（1）反射光线位于入射面内。

光学纯对映体英文

光学纯对映体英文## Enantiomers and Optical Purity.In the realm of chemistry, chirality refers to the property of a molecule that lacks mirror symmetry, muchlike our left and right hands. Chiral molecules exist in two distinct forms known as enantiomers, which are mirror images of each other but cannot be superimposed. Enantiomers are like two non-identical twins, sharing the same molecular formula and connectivity but differing in their spatial arrangement.Optical purity, a crucial concept in stereochemistry, quantifies the enantiomeric excess of a chiral compound. It measures the proportion of one enantiomer relative to the other in a mixture. A mixture containing equal amounts of both enantiomers is considered racemic and has an optical purity of 0%. Conversely, a mixture containing only one enantiomer is optically pure and has an optical purity of 100%.### Separation of Enantiomers.The separation of enantiomers is a challenging yet essential task in many fields, including pharmaceuticals, agrochemicals, and fragrances. Various techniques can be employed to achieve this, including:Chiral chromatography: This technique utilizes achiral stationary phase that interacts differently with different enantiomers, allowing for their separation.Chiral resolution: This involves converting a racemic mixture into a pair of diastereomers, which can then be separated by conventional methods.Enzymatic resolution: Enzymes, being chiral themselves, can selectively catalyze reactions with one enantiomer over the other, leading to the formation of optically pure products.### Optical Purity Measurement.Optical purity can be determined using various methods, such as:Polarimetry: This technique measures the rotation of plane-polarized light as it passes through a chiral sample. The magnitude and direction of rotation depend on the enantiomeric composition of the sample.NMR spectroscopy: Chiral solvents or chiral shift reagents can be used in NMR spectroscopy to differentiate between enantiomers based on their different chemical shifts.Chromatographic methods: Chiral chromatography or capillary electrophoresis can be used to separate enantiomers and determine their relative abundance.### Significance of Optical Purity.Optical purity is of paramount importance in several areas:Pharmacology: Many drugs are chiral, and their enantiomers can have different pharmacological properties, including efficacy, toxicity, and metabolism. Enantiopure drugs offer advantages in terms of safety and effectiveness.Agrochemicals: Herbicides and pesticides can be chiral, and their enantiomers may differ in their selectivity and environmental impact. Optical purity ensures the targeted control of pests and weeds.Fragrances and flavors: The fragrance and flavor of chiral compounds can depend on their enantiomeric composition. Optical purity control allows for the creation of specific scents and tastes.### Applications of Chiral Compounds.Chiral compounds find widespread applications invarious industries:Pharmaceuticals: Enantiopure drugs include ibuprofen,naproxen, and thalidomide.Agrochemicals: Herbicides such as glyphosate and pesticides like cypermethrin are chiral.Fragrances and flavors: Enantiopure compounds like menthol, camphor, and limonene contribute to thedistinctive scents and tastes of products.Materials science: Chiral polymers, liquid crystals, and self-assembling systems have unique properties and applications in optics, electronics, and nanotechnology.### Conclusion.The concept of enantiomers and optical purity is crucial for understanding the stereochemistry of chiral compounds. The ability to separate and determine the optical purity of enantiomers is essential in numerous fields, including pharmaceuticals, agrochemicals, and fragrances. The significance of optical purity lies in itsimplications for the safety, efficacy, and properties of chiral compounds in various applications.。

Exploring the Optical Properties of Materials

Exploring the Optical Properties ofMaterialsMaterials can have a range of optical properties, depending on their composition, structure, and interactions with light. Understanding these properties can help us develop new materials for a variety of applications, from optical data storage to solar cells.One of the most fundamental optical properties of materials is their refractive index, which describes how much the speed of light is reduced when it travels through the material. This property is determined by the electronic and atomic structure of the material, as well as the density and arrangement of its atoms.Another important optical property is absorption, which occurs when a material absorbs certain wavelengths of light and re-emits the energy as heat or fluorescence. Different materials absorb light differently depending on their electronic structure and the energy of the incoming photons. This property is useful in applications like photovoltaics, where materials that absorb certain wavelengths of light well can be used to convert that light into energy.Reflection is also an important optical property. When light hits a surface, some of it is reflected back and some of it is transmitted through. The amount that is reflected depends on the angle of incidence, the polarization of the light, and the roughness of the surface. This property is important in applications like mirrors and optical coatings, where materials that reflect light well are desired.The interaction of materials with light can also cause them to emit their own light in a process called luminescence. This property can be used in applications like lighting and imaging, where materials that emit light in certain wavelengths are desired. Luminescence can also be used to study the electronic structure of materials, as different materials emit light in different ways.Understanding the optical properties of materials is also important for developing new technologies like optical computing and communication. Light can be used to carry information through optical fibers, which have low absorption and high reflection properties. Optical materials can also be used to manipulate or modulate light signals, allowing for the development of new optical devices.Overall, the exploration of optical properties in materials is a fascinating field that offers endless possibilities for new technologies and applications. By understanding how materials interact with light, we can develop new materials that can convert, manipulate, and transmit light in exciting and useful ways.。

光的衍射英语作文

光的衍射英语作文Diffraction of Light。

Light is a fascinating phenomenon that plays a crucial role in our everyday lives. One of the most intriguing aspects of light is its ability to diffract, or bend, when it encounters an obstacle or passes through a narrow opening. This phenomenon, known as light diffraction, has been studied and observed for centuries, leading to a better understanding of the nature of light and its behavior.When light waves encounter an obstacle or a slit that is comparable in size to the wavelength of the light, diffraction occurs. This causes the light waves to bend around the edges of the obstacle or slit, creating a pattern of light and dark fringes on a screen placed behind the obstacle. This pattern, known as a diffraction pattern, is a result of the interference of the diffracted light waves.The diffraction of light can be observed in various everyday situations. For example, when light passes through a small opening, such as a pinhole or the aperture of a camera, it diffracts and creates a blurry image. This is why pinhole cameras produce images with a soft focus and why the edges of shadows appear fuzzy.In addition to being a fascinating phenomenon, light diffraction also has practical applications in various fields. In optics, diffraction gratings are used to disperse light into its component colors, allowing scientists to study the spectral properties of light. In astronomy, diffraction is used to analyze the light emitted by stars and galaxies, providing valuable information about their composition and temperature.Furthermore, the study of light diffraction has led to the development of technologies such as holography, which relies on the interference patterns created by diffracted light waves to produce three-dimensional images. Holograms are used in security features on credit cards, passports, and other important documents, as they are difficult to replicate or counterfeit.In conclusion, the phenomenon of light diffraction is a fascinating and important aspect of the behavior of light. By studying and understanding the principles of light diffraction, scientists and researchers have been able to make significant advancements in various fields, from optics to astronomy to technology. The study of light diffraction continues to be an exciting and fruitful area of research, with new discoveries and applications constantly emerging.。

InGaAs

第 21 卷第 12 期2023 年 12 月Vol.21，No.12Dec.，2023太赫兹科学与电子信息学报Journal of Terahertz Science and Electronic Information TechnologyInGaAs/InAlAs光电导太赫兹发射天线的制备与表征陈益航1，杨延召2，张桂铭2，徐建星1，苏向斌1，王天放1，余红光1，石建美1，吴斌2，杨成奥1，张宇1，徐应强1，倪海桥1，牛智川1(1.中国科学院半导体研究所，北京100083；2.中国电子科技集团公司第四十一研究所，山东青岛266555)摘要：光电导天线作为太赫兹时域光谱仪产生与探测太赫兹辐射的关键部件，具有重要的科研与工业价值。

本文采用分子束外延(MBE)方法制备InGaAs/InAlAs超晶格作为1 550 nm光电导天线的光吸收材料，使用原子力显微镜、光致发光、高分辨X射线衍射等方式验证了材料的高生长质量；通过优化制备条件得到了侧面平整的台面结构光电导天线。

制备的光电导太赫兹发射天线在太赫兹时域光谱系统中实现了4.5 THz的频谱宽度，动态范围为45 dB。

关键词：太赫兹时域光谱仪；光电导天线；分子束外延；InGaAs/InAlAs超晶格中图分类号：TN405.98+.4文献标志码：A doi：10.11805/TKYDA2022204Fabrication and characterization of InGaAs/InAlAs photoconductiveterahertz transmitting antennaCHEN Yihang1，YANG Yanzhao2，ZHANG Guiming2，XU Jianxing1，SU Xiangbin1，WANG Tianfang1，YU Hongguang1，SHI Jianmei1，WU Bin2，YANG Cheng'ao1，ZHANG Yu1，XU Yingqiang1，NI Haiqiao1，NIU Zhichuan1(1.Institute of Semiconductors，Chinese Academy of Science，Beijing 100083，China；2.The 41st Institute of China Electronic Technology Group Corporation，Qingdao Shandong 266555，China)AbstractAbstract：：Photoconductive antennas are of great scientific and industrial value as the key components for generating and detecting terahertz radiation in terahertz time-domain spectrometers. Inthis paper, Molecular Beam Epitaxy(MBE) is utilized to prepare InGaAs/InAlAs superlattices as light-absorbing materials for 1 550 nm photoconductive antennas. The high growth quality of the materials isverified by Atomic Force Microscopy(AFM), Photoluminescence(PL), and high-resolution X-raydiffraction. The mesa-structured photoconductive antenna with flat sides is obtained by optimizing thepreparation conditions. The fabricated photoconductive terahertz transmitting antenna achieves aspectral width of 4.5 THz in a terahertz time-domain spectroscopy system with a dynamic range of 45 dB.KeywordsKeywords：：terahertz time-domain spectrometer；photoconductive antenna；Molecular Beam Epitaxy；InGaAs/InAlAs superlattices太赫兹时域光谱基于超短太赫兹脉冲的相干时间分辨探测原理工作，是重要的材料分析检测技术，也是开展太赫兹频段科学研究的关键平台[1]。

applied optics

applied opticsApplied OpticsIntroductionOptics, the branch of physics that involves the behavior and properties of light, has been an important field of study for many centuries. Over the years, advancements in optics have led to various applications in different fields, giving rise to the discipline of applied optics. Applied optics focuses on the practical applications of optical principles and techniques in areas such as telecommunications, imaging, laser technology, and more. This document aims to provide an overview of applied optics, discussing some of its key concepts and applications.Basic Principles of OpticsBefore delving into the applications of optics, it is essential to understand some basic principles. Optics primarily deals with the behavior of light, which can be described as both a particle and a wave. The wave nature of light is governed by phenomena such as diffraction and interference, while itsparticle nature is manifest in phenomena like reflection and refraction.Refraction, for example, occurs when light passes from one medium into another and changes direction. This phenomenon is utilized in a variety of applications, such as the creation of eyeglasses and lenses. Reflection, on the other hand, is the bouncing back of light from a surface. It plays a crucial role in the design of mirrors and optical devices like telescopes.Applications of Applied Optics1. TelecommunicationsOne of the significant applications of optics is in the field of telecommunications. Optical fibers, which are thin strands of glass or plastic, are used to transmit information over long distances through the principle of total internal reflection. These fibers are capable of carrying large amounts of data at ultra-fast speeds. The use of optics in telecommunications has revolutionized the way we communicate, enabling high-speed internet connections, video conferencing, and more.2. Imaging and PhotographyOptics is essential in the field of imaging and photography. Camera lenses utilize the principles of refraction and focusing to capture sharp and clear images. The aperture, focal length, and lens design all contribute to the image quality and depth of field. Optics also plays a role in scientific imaging techniques like microscopy and telescopes, allowing for the observation of microscopic and distant objects with high precision.3. Laser TechnologyLasers, an acronym for Light Amplification by Stimulated Emission of Radiation, are devices that generate a coherent and focused beam of light. The principles of optics are fundamental to the functioning of lasers. The applications of laser technology range from industrial manufacturing and cutting to medical procedures and scientific research. Lasers have also found applications in data storage, barcode scanning, and optical communication.4. Optical MetrologyOptical metrology involves the measurement and analysis of objects using optical principles and techniques. This field encompasses various measurement techniques such as interferometry, spectrometry, and profilometry. Optical metrology finds applications in manufacturing quality control, material characterization, and dimensional measurements. It offers high accuracy and non-contact measurement methods, making it indispensable in various industries.5. Biomedical OpticsThe application of optics in the field of medicine has contributed to significant advancements in diagnostics and treatment. Biomedical optics involves the use of optical techniques to study biological tissues, cells, and molecules. Techniques such as optical coherence tomography (OCT) and fluorescence imaging have revolutionized medical imaging, allowing for non-invasive and high-resolution visualization of tissues and organs. Optical techniques are also utilized in laser surgery, photodynamic therapy, and bio sensing.ConclusionApplied optics is a discipline that is at the forefront of technological innovation and contributes to various fields,including telecommunications, imaging, laser technology, optical metrology, and biomedical optics. Its applications have revolutionized industries, improved medical diagnostics, and enhanced our ability to communicate and explore our surroundings. With further advancements in optical principles and techniques, the future of applied optics is promising, and it will continue to have a significant impact on science and technology.。

Measuring the Optical Properties of Materials

Measuring the Optical Properties ofMaterialsThe optical properties of materials refer to how they interact with light. These properties are important in many applications, from designing new materials for optical devices to understanding the behavior of light in biological systems. Measuring these properties requires specialized equipment and techniques, which we will discuss in this article.Absorption and TransmissionOne of the primary optical properties of materials is their absorptivity and transmissivity. Absorbance refers to the amount of light that a material absorbs, while transmittance refers to the amount of light that passes through the material. A material that is highly absorptive will appear darker in color, while a material that is highly transmissive will appear clearer.To measure these properties, researchers use a spectrophotometer, which measures the amount of light absorbed or transmitted by a material at different wavelengths. A sample is placed in the spectrophotometer, and a light source produces a range of wavelengths. The amount of light that passes through the sample is measured, and the results are recorded on a graph.Refraction and ReflectionAnother important optical property is a material's ability to refract or bend light rays. This property is known as refractive index. The refractive index of a material determines how much the angle of a light ray changes when it enters the material, and it plays a critical role in the design of lenses and other optical devices.Reflection is also an important property of materials, especially those used in mirrors and other reflective surfaces. A material's reflectivity determines how much light isreflected off its surface, and this property is measured using a reflectometer. This instrument measures the intensity of light reflected off a material at a specific angle.Fluorescence and PhosphorescenceFluorescence and phosphorescence are two other important optical properties of materials. Fluorescence refers to the emission of light from a material after it has been excited by an external energy source, such as light or heat. Phosphorescence is a similar process, but the emission of light continues after the external energy source has been removed. These properties are commonly observed in biological molecules and dyes, and they are used in many applications, including fluorescence microscopy and forensics.To measure these properties, researchers use a fluorometer, which measures the intensity of emitted light at different wavelengths. A sample is excited by a light source, and the resulting fluorescence or phosphorescence is measured and recorded on a graph.ConclusionMeasuring the optical properties of materials is essential for a wide range of applications, from designing new materials for optical devices to understanding light's behavior in biological systems. The properties discussed in this article, including absorption, transmission, refraction, reflection, fluorescence, and phosphorescence, are essential for understanding how materials interact with light. By using specialized equipment and techniques, researchers can measure these properties accurately and use them to design new materials and technologies.。

光电直读发射光谱法和电感耦合等离子体原子发射光谱法

光电直读发射光谱法和电感耦合等离子体原子发射光谱法下载温馨提示:该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。

文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by theeditor.I hope that after you download them,they can help yousolve practical problems. The document can be customized andmodified after downloading,please adjust and use it according toactual needs, thank you!In addition, our shop provides you with various types ofpractical materials,such as educational essays, diaryappreciation,sentence excerpts,ancient poems,classic articles,topic composition,work summary,word parsing,copy excerpts,other materials and so on,want to know different data formats andwriting methods,please pay attention!光电直读发射光谱法与电感耦合等离子体原子发射光谱法的探析在现代科学分析领域，光电直读发射光谱法（AES）和电感耦合等离子体原子发射光谱法（ICP-AES）是两种广泛使用的元素定量分析技术。

Novel materials for optical sensing

Novel materials for optical sensingIn recent years, optical sensing has gained increasing attention due to its high sensitivity, specificity, and non-invasiveness. Optical sensing has a wide range of applications, such as environmental monitoring, biomedical diagnosis, food safety detection, and industrial process control. However, the performance of optical sensors highly depends on the properties of the sensing materials. Therefore, the development of novel materials for optical sensing is essential for achieving improved sensitivity, selectivity, and stability in optical sensing.Metal-Organic Frameworks (MOFs) is a class of porous materials composed of metal ions or clusters coordinated with organic ligands. MOFs possess high surface area, tunable pore size, and diverse chemistry, which make them attractive candidates for optical sensing. A variety of MOFs have been developed for sensing applications, such as CO2, H2O, volatile organic compounds (VOCs), and heavy metal ions. For example, the copper-based MOF, HKUST-1, has been demonstrated as a highly sensitive and selective sensor for detecting NH3 gas. The mechanism behind this sensing behavior is attributed to the reversible coordination between the NH3 and the copper center, which leads to a change in the electronic structure and optical response of the MOF.Quantum dots (QDs) are semiconductor nanocrystals with unique optoelectronic properties, including high fluorescence quantum yield, narrow emission spectra, and size-tunable photoluminescence. QDs have been widely used as fluorescent probes for biological and chemical sensing due to their superior optical properties. For instance, CdSe/ZnS QDs have been explored for sensing metal ions, such as Hg2+, Cu2+, andFe3+. The sensing mechanism is based on the fluorescence quenching or enhancement of the QDs upon the interaction with the metal ions, which is related to the charge transfer or energy transfer process in the QD-metal ion system.Graphene and its derivatives have attracted considerable attention in recent years due to their unique electronic, mechanical, and optical properties. Graphene oxide (GO) is a water-soluble and biocompatible derivative of graphene, which has been utilized foroptical sensing applications due to its excellent fluorescence quenching ability and large surface area. GO-based sensors have been developed for detecting a wide range of analytes, such as metal ions, glucose, and DNA. The interaction between the analyte and GO leads to either fluorescence quenching or enhancement, depending on the nature and concentration of the analyte.In summary, the development of novel materials for optical sensing is a rapidly growing research area that plays a critical role in advancing the performance and reliability of optical sensors. Metal-Organic Frameworks, Quantum dots, and graphene derivatives are promising materials for optical sensing with unique optical, chemical, and mechanical properties. Further research and development of these materials will facilitate the realization of more sensitive, selective, and reliable optical sensors for various applications.。

211126646_葛根蛋白分离鉴定及其自组装纳米颗粒性质研究

林岱，高观祯，周建武，等. 葛根蛋白分离鉴定及其自组装纳米颗粒性质研究[J]. 食品工业科技，2023，44（9）：20−26. doi:10.13386/j.issn1002-0306.2022100193LIN Dai, GAO Guanzhen, ZHOU Jianwu, et al. Isolation and Characterization of a Pueraria lobata Protein and Its Self-assembled Nanoparticles Properties[J]. Science and Technology of Food Industry, 2023, 44(9): 20−26. (in Chinese with English abstract). doi:10.13386/j.issn1002-0306.2022100193· 青年编委专栏—食品营养素包埋与递送（客座主编：黄强、蔡杰、陈帅） ·葛根蛋白分离鉴定及其自组装纳米颗粒性质研究林　岱1,2，高观祯2，周建武2, *，柯李晶2，饶平凡2（1.福建医科大学公共卫生学院，福建福州 350122；2.浙江工商大学食品与生物工程学院，浙江杭州 310018）摘　要：目的：纯化并表征一种葛根水溶性蛋白，将该蛋白通过热诱导的方式构建为蛋白纳米颗粒载体。

方法：采用阴离子交换色谱High Q 纯化获得葛根蛋白，通过SDS-PAGE 和蛋白质N 端测序方法鉴定蛋白的分子量和氨基酸序列。

采用激光粒度分析仪对蛋白纳米颗粒的粒径、光散射强度和Zeta 电位进行研究，采用高效液相色谱法测定纳米载体对药物的装载效率。

结果：从葛根中抽提并分离纯化获得一种主要的水溶性蛋白，命名为PP 。

N-端氨基酸序列测得为DFVYDMCGNVLNGGTYYIL ，通过NCBI 数据库比对和蛋白酶活性测定确定PP 为一种新的胰蛋白酶抑制剂，且PP 在pH2~10的环境中及20~50 ℃的温度范围内均具有较好的稳定性。

AppliedOpticsReviewCriteria

Applied OpticsReview CriteriaApplied Optics publishes peer-reviewed articles related to applications-centered research in optics, photonics, imaging, and sensing. Articles should concentrate on moving the potential of science and technology to the practical. Articles introduce new science or technology in an optics discipline in the form of increased understanding or a novel application of an existing topic. Articles are in-depth and should include the development and performance of technologies when applying theories.To meet Applied Optics goal of publishing timely and high-impact research, submitted papers are subjected to critical review according to the criteria listed below.Appropriateness for Applied OpticsDoes the subject material fall within the scope of the journal? Will the paper be of interest to the applied optics community?Rating Options: Very high, High, Moderate, Low, Very lowQuality, Depth, and Completeness of ContentDoes the manuscript provide increased understanding related to the applications of optics, photonics, sensing, or imaging? Is the paper an original and significant contribution to the field? Is the topic covered in depth? Is the topic covered completely, e.g., theory, simulation, experimentation, and analysis?Does the topic provide design guidelines or explain limitations on implementations of theory? Are the conclusions supported by the data presented, and is the work placed in proper context? Is prior or related work adequately referenced? Note that papers considered to be incremental, incomplete, or lacking in scientific or technical relevance are likely to be rejected. Does the work warrant publication in an archival journal?Rating Options: Very high, High, Moderate, Low, Very lowSignificanceReviewers are asked to rate the significance of submitted papers assuming appropriate revisions are made. What likely impact will the submitted paper have on the research field covered? Significant papers are expected to explore unanswered practical issues. They can make an impact through novel results, in-depth analysis, address important problems, provide new theoretical insights, or present clear methods, procedures, or reviews to help other researchers perform similar work.Rating Options: High, Moderate, LowQuality of PresentationIs the title accurate and does it clearly identify the subject matter? Is the abstract succinct and comprehensible to a non-specialist? Is the manuscript clearly written and logically organized? Are figures and tables understandable and readable as submitted, including all captions and labels? Is the quality of English language usage and grammar appropriate for an archival journal (note that Applied Optics articles are minimally copy-edited)? If there is multimedia content, is it clearly presented and does it contribute to presentation of the research? Is the manuscript formatted according to the journal style guide? Are the OCIS codes selected by the authors appropriate for indexing the article?Rating Options: Very high, High, Moderate, Low, Very lowManuscripts judged by reviewers as moderate in the first three criteria (appropriateness, technical quality & completeness, and significance) will not be accepted for publication in Applied Optics.。

Ultrasonic Imaging Advances and Applications

Ultrasonic Imaging Advances and Applications Ultrasonic imaging has made significant advances in recent years, revolutionizing medical diagnostics and opening up new possibilities for non-destructive testing in various industries. This technology, which utilizes high-frequency sound waves to create images of internal body structures or objects, has become an indispensable tool in the medical field, allowing for more accurate and early detection of diseases and abnormalities. In addition to its medical applications, ultrasonic imaging is also being increasingly used in industrial and environmental settings, further expanding its potential impact on society.One of the key advancements in ultrasonic imaging is the development of 3D and 4D imaging techniques. Traditional 2D ultrasound images provide valuable information, but they are limited in their ability to convey the spatial relationships and depth of structures within the body. With 3D and 4D imaging, healthcare providers can now obtain a more comprehensive view of the internal organs and tissues, leading to improved diagnostic accuracy and better treatment planning. This has been particularly beneficial in obstetrics, where 3D and 4D ultrasound technology allows for detailed visualization of the fetus, aiding in the early detection of abnormalities and enhancing the bonding experience for expectant parents.Furthermore, the integration of artificial intelligence (AI) and machine learning algorithms has significantly enhanced the capabilities of ultrasonic imaging. These technologies have enabled the development of automated image analysis tools that can assist healthcare providers in interpreting ultrasound images more efficiently and accurately. By leveraging AI, it is now possible to detect subtle anomalies that may have been overlooked in the past, ultimately leading to earlier intervention and improved patient outcomes. In addition to medical applications, AI-powered ultrasonic imaging systems are also being used in industrial settings for defect detection and quality control, demonstrating the versatility and potential of this technology across different sectors.Another notable advancement in ultrasonic imaging is the miniaturization of ultrasound devices, leading to the development of portable and handheld ultrasound systems. These compact and lightweight devices have revolutionized point-of-care imaging,allowing healthcare providers to perform ultrasound examinations directly at the patient's bedside. This has proven to be particularly valuable in emergency and critical care settings, where timely access to diagnostic information is crucial for making informed clinical decisions. The portability of these devices has also extended the reach of ultrasound imaging to underserved and remote communities, enabling more people to benefit from this essential diagnostic modality.In addition to medical and industrial applications, ultrasonic imaging has also found a niche in the field of veterinary medicine. Veterinarians are increasingly utilizing ultrasound technology for diagnostic imaging in small and large animals, providing valuable insights into the health and well-being of their patients. From detecting pregnancy in livestock to diagnosing soft tissue injuries in companion animals, ultrasonic imaging has become an indispensable tool for veterinary practitioners, contributing to improved animal care and welfare.Despite these advancements, challenges remain in the widespread adoption and accessibility of ultrasonic imaging technology. Cost is a significant barrier, particularly in resource-limited settings where the initial investment and ongoing maintenance of ultrasound equipment can be prohibitive. Efforts to make ultrasonic imaging more affordable and accessible, especially in low-income countries, are crucial for ensuring equitable healthcare and improving health outcomes globally. Additionally, ongoing research and development are needed to further enhance the capabilities of ultrasonic imaging, particularly in areas such as contrast-enhanced ultrasound and functional imaging modalities.In conclusion, ultrasonic imaging has undergone significant advancements, transforming medical diagnostics, industrial testing, and veterinary medicine. From 3D and 4D imaging to the integration of AI and portable ultrasound devices, this technology has expanded its reach and potential impact across various domains. While challenges persist, the continued innovation and investment in ultrasonic imaging hold great promise for improving healthcare delivery, enhancing diagnostic accuracy, and ultimately benefiting individuals and communities worldwide.。

光纤锥耦合

August1,1997/Vol.22,No.15/OPTICS LETTERS1129 Phase-matched excitation of whispering-gallery-moderesonances by a fiber taperJ.C.Knight,G.Cheung,F.Jacques,and T.A.BirksOptoelectronics Group,School of Physics,University of Bath,Bath BA27AY,UKReceived April14,1997We show that high-Q whispering-gallery modes in fused-silica microspheres can be efficiently excited by anoptical fiber taper.By adjusting the taper diameter to match the propagation constant of the mode in thetaper with that of the resonant mode of interest,one can couple more than90%of the light into the sphere.This represents a significant improvement in excitation efficiency compared with other methods and is,webelieve,the most efficient excitation of a high-Q microcavity resonance by a monomode optical fiber yet demonstrated.©1997Optical Society of AmericaWhispering-gallery-mode(WGM)resonances are elec-tromagnetic resonances that occur in circularly sym-metric dielectric particles.1They correspond to light trapped in circling orbits just within the surface of the particle,being continuously totally internally ref lected from the surface.Under these circumstances the leak-age of light from the particle can be extremely low. The high-Q values and small mode volumes of these WGM resonances in fused-silica microspheres make this system of interest for a number of fundamental and applied studies.1–3A crucial point of these studies is that one needs to be able to couple light into and out of the cavity.Braginsky et ed prism coupling to excite the modes.2Using total internal ref lection, one produces an evanescent field at the surface of a high-index prism,with the angle of incidence upon the internal surface of the prism chosen to match the propagation constant with that required for excitation of the mode of interest.Hence one is coupling a large number of free-space modes into the resonant mode of interest.This method is f lexible and can be made ef-ficient,but it is bulky and awkward.Other workers have used a side-polished optical fiber as an excitation source.4,5This method has the advantage that the ex-citation source is an optical fiber and is thus convenient to use.Furthermore,the propagation constant in the core of a silica-based optical fiber will always be clos-est to that of the lowest radial mode number WGM,1 which(as described below)is the mode with the most desirable properties.However,this matching is per-fect only in the limit of large sphere size,limiting the attainable coupling efficiency toϳ20%for very large spheres,of diameter1mm,and to much less for smaller spheres.4In this Letter we report that,by replacing the side-polished fiber with an adiabatically tapered fiber,we can maintain several of the advantages of the side-polished fiber source while coupling light with high efficiency to any particular mode of interest,in spheres with a wide range of sizes.We refer to a homogeneous fiber taper of radius r and a sphere of size parameter x෇2p a͞l(where a is the sphere radius and l is the wavelength of the light in free space).To determine the size of fiber taper required for efficient excitation of the chosen WGM we need to match the propagation constant of the WGM at the surface of the sphere to the propagation constant of the appropriate mode in the tapered fiber. The WGM is characterized by the mode numbers n, l,and m,the radial,angular,and azimuthal mode numbers,respectively.1To maximize the advantage of a microcavity resonance we are interested in exciting modes with low n and with mХl.These are the modes with the smallest mode volume,as they are most closely confined to the surface of the sphere (lowest radial mode number n)and to the sphere equator͑j m j෇l͒.In this case we can approximate the propagation constant b by b෇kl͞x nlm,where x nlm is the size parameter that corresponds to the n,l,and m resonance and k is the free-space propagation constant. This formula gives the correct value because2l is the number of maxima in the angular variation of the resonant field around the microsphere equator. For large spheres and for the lowest radial mode number b approaches the propagation constant in pure silica,but for smaller spheres it quickly becomes significantly smaller.Here we calculate the values of l that correspond to the various values of n for a sphere of a given size a and refractive index N in the wavelength region of interest,using the approximate expressions described by Schiller.6We form a fiber taper by heating and stretching a section of optical fiber to form a narrow thread,or waist,which is joined to the untreated ends of the fiber by a gradual taper transition.7In the waist region the fiber core is no longer significant,and the light travels in the fundamental mode along the waveguide formed by the silica waist surrounded by air.The taper waist can be as little as a micrometer in diameter.On reaching the other end of the waist,the light remaining in the waist is returned to the guided mode in the fiber core.If the waist is small,the fundamental mode will have an evanescent tail extending significantly out into the free space surrounding the taper,and the propagation constant of the mode will be a function of the waist radius.For the radii of interest here this dependence can be expressed asb2෇k2N22͑2.405͒2͞r2,(1)0146-9592/97/151129-03$10.00/0©1997Optical Society of America1130OPTICS LETTERS/Vol.22,No.15/August1,1997where k is the free-space propagation constant of the light.For the taper diameters used in our experi-ments(with1.4m m,r,3m m)this approximation is in error by less than1%compared with the exact values.8Some results of the phase-matching calculations are shown in Fig.1.The solid curve represents the propa-gation constant b of the fundamental taper mode [Eq.(1)]as a function of the radius(top axis).The points are plotted on the lower axis and show the propagation constants of the lowest few radial mode numbers for several different sphere diameters(differ-ing l)in the wavelength range of interest.The top and bottom scales in the plot have been chosen to match ap-proximately the b for a given taper size(on the top scale)with that of the lowest radial mode number mode in a particular size of sphere(on the bottom scale).A relatively small range of taper sizes is seen to match the propagation constants over a wide range of sphere sizes.Because the interaction length is limited by the curvature of the microsphere surface,the overall cou-pling is not expected to be sensitive to small varia-tions in the taper diameter or sphere size.Coupling to higher-n modes in a sphere of a given size would re-quire smaller taper diameters.The tapered fibers used in our experiments were formed from lengths of standard telecommunications fiber(which guides a single mode at the wavelengths near1550nm used in these experiments).The poly-mer coating was stripped from a short length of the fiber.The fiber was then heated with a traveling f lame while being drawn gradually to be stretched to the desired size.By monitoring the light through the fiber while the drawing proceeded we were able to en-sure that the overall losses from the taper were kept at the level of0.1dB.The heated length of fiber and the draw extension are controlled by a computer and are chosen to result in a taper waist of the required diameter.The accuracy of the resulting waist diame-ter is of the order of5%.After fabricating the taper we mounted it horizontally by suspending it at both ends so that it could be drawn taught.We formed a fused-silica microsphere by f lame fusing the end of a fine silica wire.The wire remained attached to the sphere,and resonances were excited in the equatorial plane perpendicular to the wire axis.The sphere was mounted upon x–y–z microcontrols to bring the sphere equator region into contact with the tapered fiber.A tunable single-mode diode laser(with lഠ1550nm and DnХ3MHz)was coupled into one end of the tapered fiber while the fiber throughput was monitored with a photodiode(PD)at the far end.The experiment is shown schematically in Fig.2(a).When the laser wavelength was scanned past a mi-crosphere resonance,a dip appeared in the transmit-ted light.Examples of such resonances are shown in Fig.2(b).The main trace shows a sphere of size aХ85m m͑xХ350͒excited with a taper of rХ1.7m m. More than72%of the light in the fiber is coupled out on resonance,and the cavity Q value is Q෇23106. Off resonance,only a negligible fraction of the light in the fiber͑,,1%͒is coupled out by the presence of the sphere.The oscillations on the off-resonant trans-mission signal are caused by the ref lections from the fiber ends and are not related to the presence of the microsphere;the slope on the curve is due to the vari-ation of the power in the fiber while the wavelength is scanned.The amplitude of the dip depends on the alignment of the fiber and the sphere as well as on the particular mode being excited:we observed a dip of more than90%of the off-resonance transmission when we used a somewhat larger sphere,of radius210m m, with QХ1.53106.The inset shows a mode in this larger sphere excited by a taper of rХ2.25m m.The measured linewidth corresponds to a Q ofϳ53107 and is due entirely to the acoustic linewidth of our laser source.In principle there is no reason why Q factors as high as1011could not be observed likethis, Fig.1.Calculated values of the propagation constants for a fiber taper(solid curve)as a function of the radius (plotted on the top axis)and for the first few radial mode numbers of WGM resonance for spheres of different sizes, plotted on the loweraxis.Fig.2(a)Schematic representation of the experiment. The microsphere is mounted upon x–y–z micropositioners to allow it to be manipulated with respect to the tapered fiber.(b)Example of a resonance dip appearing on the transmission signal.In this case72%of the light is coupled into the resonance,which has a Q of23106.The sphere size is aХ85m m,and the taper size is rХ1.7m m. The inset shows a narrower mode in a larger sphere with a larger taper radius(aХ210m m,rХ2.25m m,Q෇53107, excitation efficiency37%).August1,1997/Vol.22,No.15/OPTICS LETTERS1131provided that proper precautions were taken.9Al-though the presence of the tapered fiber in the mode volume couples light out of the microcavity resonance, causing it to be broadened,and although it is not pos-sible to control accurately the gap between the fiber and the microsphere,it is nonetheless possible to con-trol the spacing between the fiber and the mode vol-ume,which occupies only a spatially localized region on the microsphere surface.10When the sphere is in the overcoupled regime(when losses that are due to the presence of the fiber dominate the resonance linewidth)one might expect to see a substantial decrease in the dip on the transmission signal as the light coupled out of the sphere is returned to the fiber guided mode.11Although we do indeed see such a decrease,it varies from a few to perhaps a few tens of percent and is not nearly so substantial as expected.This finding indicates that the light coupled out of the sphere is not all reentering the fundamental fiber mode,which is surprising given the efficient coupling into the sphere and may indicate that we are exciting lﬁj m j modes in the sphere at present.This phenomenon will be the subject of further investigation.On the other hand,even at the lowest observed Q when we can couple into the mode efficiently,the light is traveling some tens of centimeters and making several hundred round trips inside the cavity.The ability to couple light in an efficient manner directly from a monomode optical fiber into a high-Q microsphere resonance is essential if microspheres are to be used in optoelectronic devices such as filters and fiber-coupled microlasers.References1.See,e.g.P.W.Barber and R.K.Chang,eds.,OpticalEffects Associated with Small Particles(World Scien-tific,Singapore,1988);R.K.Chang and A.J.Campillo, eds.,Optical Processes in Microcavities(World Scien-tific,Singapore,1996).2.V.B.Braginsky,M.L.Gorodetsky,and V.S.Ilchenko,Phys.Lett.A137,393(1989).3.L.Collot,V.Lef´e vre-Seguin,M.Brune,J.M.Raimond,and S.Haroche,Europhys.Lett.23,327(1993);D.W.Vernooy and H.J.Kimble,Phys.Rev.A55,1239(1997).4.A.Serpenguzel,S.Arnold,and G.Griffel,Opt.Lett.20,654(1995);G.Griffel,S.Arnold,D.Taskent,A.Serpenguzel,J.Connolly,and N.Morris,Opt.Lett.21, 695(1996).5.N.Dubreuil,J. C.Knight, D.Leventhal,V.Sandoghdar,J.Hare,and V.Lef´e vre,Opt.Lett.20,813(1995).6.S.Schiller,Appl.Opt.32,2181(1993).7.K.P.Jedrzejewski,F.Martinez,J.D.Minelly,C.D.Hussey,and J.P.Payne,Electron.Lett.22,105(1986).8.A.W.Snyder and J. D.Love,Optical WaveguideTheory(Chapman&Hall,London,1988);Croix, D´e partement de G´e nie Physique,E´c ole Polytech-nique de Montreal,P.O.Box6079,Montr´e al,Quebec, H3C3A7Canada(personal communication,1997).9.M.L.Gorodetsky,A.A.Savchenkov,and V.S.Ilchenko,Opt.Lett.21,453(1996).10.J.C.Knight,N.Dubreuil,V.Sandoghdar,J.Hare,V.Lef´e vre-Seguin,J.M.Raimond,and S.Haroche,Opt.Lett.20,1515(1995).11.S.Schiller,I.I.Yu,M.M.Fejer,and R.L.Byer,Opt.Lett.17,378(1992).。

Negative index of refraction in optical metamaterials

$Negative index of refraction in optical metamaterials$

Negative index of refraction in opticalmetamaterialsVladimir M.Shalaev,Wenshan Cai,Uday K.Chettiar,Hsiao-Kuan Yuan,Andrey K.Sarychev,Vladimir P.Drachev,and Alexander V.KildishevSchool of Electrical and Computer Engineering,Purdue University,West Lafayette,Indiana47907Received September13,2005;accepted October14,2005A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range.Such behavior results from the plasmon resonance in the pairs of nanorods for both the elec-tric and the magnetic components of light.The refractive index is retrieved from direct phase and amplitude measurements for transmission and reﬂection,which are all in excellent agreement with simulations.Both experiments and simulations demonstrate that a negative refractive index nЈϷ−0.3is achieved at the op-tical communication wavelength of1.5␮m using the array of nanorods.The retrieved refractive index criti-cally depends on the phase of the transmitted wave,which emphasizes the importance of phase measure-ments inﬁnding nЈ.©2005Optical Society of AmericaOCIS codes:160.4670,260.5740,310.6860.One of the most fundamental notions in optics is that of the refractive index,which gives the factor by which the phase velocity of light is decreased in a ma-terial compared with vacuum conditions.In materi-als with a negative refractive index the phase veloc-ity is directed against theﬂow of energy.There are no known naturally occurring negative-index materials (NIMs).Proof-of-principle experiments1have shown that artiﬁcially designed materials(metamaterials) can act as NIMs at microwave wavelengths.NIMs drew a large amount of attention after Pendry pre-dicted that NIMs can act as a superlens allowing im-aging resolution that is limited not by the wave-length but rather by material quality.2The near-ﬁeld version of the superlens has already been reported.3,4 Materials that can be characterized by a dielectric permittivity⑀=⑀Ј+i⑀Љand a magnetic permeability ␮=␮Ј+i␮Љhave a negative real part of the complex refractive index if the sufﬁcient(but not necessary) conditions⑀ЈϽ0and␮ЈϽ0are fulﬁlled.5Recent experiments showed that a magnetic re-sponse and a negative permeability can be obtained in the terahertz spectral ranges.6–8However,the ul-timate goal,a negative refractive index,was not achieved in those experiments.In parallel with progress for metal–dielectric metamaterials,two ex-perimental demonstrations of negative refraction in the near IR range have been made in GaAs-based photonic crystals9and in Si-polyimide photonic crystals.10Below we report our experimental demonstration of a negative refractive index material for the optical range,speciﬁcally for wavelengths close to1.5␮m (200THz frequency),accomplished with a metal–dielectric composite.The NIM structural design used follows our theoretical prediction of negative refrac-tion in a layer of pairs of parallel metal nanorods.11,12 For normally incident light with the electricﬁeld polarized along the rods and the magneticﬁeld per-pendicular to the pair[Fig.1(a)],the electric and magnetic responses both can experience resonant be-havior at certain frequencies.Above the resonance frequency,the circular current in the pair of rods can lead to a magneticﬁeld opposing the external mag-neticﬁeld of the light.The excitation of plasmon reso-nances for both the electric and the magnetic light components results in the resonant behavior of the refractive index,which can become negative above the resonance as previously predicted.11,12This reso-nance can be thought of as a resonance in an optical LC circuit,with the metal rods providing the induc-tance L and the dielectric gaps between the rods act-ing as capacitive elements C.Note that coupling be-tween metal rods may lead to other interesting optical properties.13We performed our experiments with a2mm ϫ2mm array of nanorods on a glass substrate fabri-cated using electron-beam lithography with a JEOL JBX-6000FS writer.To prevent a charging effect in the case of the glass substrate,a thin Cr layer was deposited on top of the double layer ofpoly(methyl-Fig.1.(a)Schematic for the array of nanorod pairs.(b) Field-emission scanning electron microscope images.(c)El-ementary cell.3356OPTICS LETTERS/Vol.30,No.24/December15,20050146-9592/05/243356-3/$15.00©2005Optical Society of Americamethacrylate)photoresist.Then,after writing, the Cr layer was removed with appropriate etching. The desired sandwich structure,Ti͑5nm͒/Au ͑50nm͒/Ti͑5nm͒/SiO2͑50nm͒/Ti͑5nm͒/Au͑50nm͒,was deposited serially in an electron-beam vacuum evaporator.The fabrication procedure resulted in a trapezoidal shape of the rods.Figure1(b)showsﬁeld-emission scanning electron microscope images of a portion of the sample and a closer view of a single pair of rods.The dimensions of the bottom rods ͑780nmϫ220nm͒and the elementary cell are shown in Fig.1(c).The top rods are smaller ͑670nmϫ120nm͒.The metalﬁlling factor is13.5%. In our simulation based on a3Dﬁnite-difference time domain(FDTD)method,14the overall geometry of the nanorods followed the trapezoidal shape of the actual sample.To simulate the permittivity of gold, the Drude model⑀Au=9.0−͑1.3673ϫ1016͒2/͓␻2 +i͑1.0027ϫ1014͒␻͔,where␻=2␲c/␭,was trans-formed into a matching Debye model.The Debye model provides excellent agreement with the mea-sured optical constants in the spectral range of inter-est.The elementary cell with xϫyϫz=1.8␮m ϫ0.64␮mϫ4␮m was illuminated by a monochro-matic plane wave at normal incidence.Since we used a uniform grid with a spatial resolution of10nm,the 5nm Ti layers were not taken into account.The thick glass layer was considered inﬁnite in the simula-tions.The reﬂected and transmitted electricﬁelds, E r and E t,are calculated for the layer of the nano-rods with normally incidentﬁeld E i.Then, r=␣E r͑−d͒/E i͑−d͒and t=␣E t͑d͒/E i͑−d͒are obtained, where␣=exp͓ik͑⌬−2d͔͒,k is the wavenumber in air,⌬=160nm,and d is the distance from the center of the layer to the evaluation planes in front and behind the sample.The distance d is chosen so that the re-ﬂected and transmitted waves(E r and E t)are plane waves with less than1%deviation in magnitudes in the evaluation planes.The complex index of refraction͑n=nЈ+inЉ͒of the nanorod layer on a substrate is found fromcos nk⌬=1−r2+n s t2͑n s+1͒t+rt͑n s−1͒,͑1͒where n s is the refractive index of the substrate(n s=1.48for our glass substrate).Speciﬁcally,we ob-tain the impedance Z=ZЈ+iZЉ(not shown here)and the refractive index of the equivalent homogeneouslayer with the same complex reﬂectance r and trans-mittance t as the actual array of nanorods.Equation (1)gives the refractive index of a thin layer of a pas-sive material(nЉϾ0and ZЈϾ0).Note that for a thin layer such retrieval can be performed unambiguously.15Since a linear polarization of light is preserved under propagation through our aniso-tropic sample,when the polarization is parallel to the main axes,we solve Eq.(1)independently for light polarized parallel and perpendicular to the nanorods. The amplitudes and phases for transmittance and reﬂectance needed for retrieval of the refractive in-dex were measured directly in our experiments.The transmission͑T=͉t͉2͒and reﬂection͑R=͉r͉2͒spectra are measured with a Lambda950spectrophotometer from Perkin-Elmer using linearly polarized light. The transmission spectra are collected at normal in-cidence,and the reﬂection spectra are measured at a small incident angle of8°.Control measurements of the reﬂectance performed with a laser source at0.5°of the incident angle show no signiﬁcant difference. The phase measurements were performed with po-larization and walk-off interferometers using tunable diode lasers.In the polarization interferometer,two optical channels have a common geometrical path and differ by the polarization of light.This allows one to measure the phase difference between orthogo-nally polarized waves⌬␾=␾ʈ−␾Ќcaused by aniso-tropy of a refractive material.The walk-off interfer-ometer has two optical channels that differ in geometrical paths;this gives a phase shift introduced by a sample͑␾s͒relative to a reference layer of air with the same thickness͑␾r͒:␦␾=␾s−␾r.The walk-off effect in calcite crystals is employed to separate the two beams and then bring them together to pro-duce interference.The instrumental error of the phase anisotropy measurement by polarization inter-ferometer is±1.7°.We note that variations in the substrate thickness do not affect the results of our phase anisotropy measurements,which is typical for common path interferometers.In the case of the walk-off interferometer,the thickness variation gives an additional source of error,causing the error for the absolute phase shift measurements to increase up to ±4°.A more detailed description of our phasemea-Fig.2.(Color online)(a)Reﬂection and transmission spec-tra:experiments(solid curves)and simulations(squares and circles).(b)Phase anisotropy⌬␸for reﬂection (squares)and transmission(circles),from experiments and simulations.Inset,absolute phase shifts␦␸in transmis-sion for the parallel(lower)and perpendicular(upper)po-larizations of light.December15,2005/Vol.30,No.24/OPTICS LETTERS3357surements will be published elsewhere.We note here that the linear polarization of light is well preserved after propagation through the sample for both light polarizations,parallel and perpendicular to the rods.Speciﬁcally,the light ellipticity (the intensity ratio for the two components)changes only from 10−3to 3ϫ10−3.Thus the method used provides direct mea-surements of the magnitude and sign of the phase shift for the two linearly polarized components of light.Figure 2shows results of our measurements of am-plitudes and phases for transmitted and reﬂected waves.The system of parallel gold nanorods shows a strong plasmonic resonance near 1.5␮m for both am-plitude [Fig.2(a)]and phase shift [Fig.2(b)]of light with the electric ﬁeld polarized parallel to the rods.For the electric ﬁeld polarized perpendicular to the rods the spectral dependences are rather ﬂat from 1to 2␮m,and the plasmon resonance occurs near 800nm (not shown).We note good agreement between our 3D FDTD simulations and experimental data.Figure 3shows the retrieved refractive index and demonstrates excellent agreement between measure-ments and simulations [Fig.3(b)].The obtainedphase shift of −61°in the light transmittance at ␭=1.5␮m is well below the phase shift in air −␾0=−40°at 1.5␮m;thus the negative phase acquired in the sample is Ϸ−21°.The refractive index is negative between 1.3and 1.6␮m,with n Ј=−0.3±0.1at ␭=1.5␮m.Note a rather high transmittance of Ϸ25%and relatively low absorption of Ϸ10%.The imagi-nary part of the refractive index also shows resonant behavior and it is large near the resonance.Our cal-culations show that by optimizing the system (e.g.,by matching impedances),the ratio of the real and imaginary parts of the refractive index can be signiﬁ-cantly increased.In conclusion,for an array of pairs of parallel gold rods,we obtained a negative refractive index of n ЈϷ−0.3at the optical communication wavelength of 1.5␮m.This new class of negative-index materials is relatively easy to fabricate on the nanoscale and opens new opportunities for designing negative re-fraction in optics.This work was supported in part by NSF-NIRT award ECS-0210445and by ARO grant W911NF-04-1-0350.V .M.Shalaev’s e-mail address is shalaev@.References1.R.A.Shelby,D.R.Smith,and S.Schultz,Science 292,77(2001).2.J.B.Pendry,Phys.Rev.Lett.85,3966(2000).3.N.Fang,H.Lee,and X.Zhang,Science 308,534(2005).4.D.O.S.Melville and R J.Blaikie,Opt.Express 13,2127(2005).5.V .G.Veselago,p.10,509(1968)[Usp.Fiz.Nauk 92,517(1964)].6.T.J.Yen,W.J.Padilla,N.Fang,D.C.Vier,D.R.Smith,J. B.Pendry, D.N.Basov,and X.Zhang,Science 303,1494(2004).7.S.Linden, C.Enkrich,M.Wegener,J.Zhou,T.Koschny,and C.Soukoulis,Science 306,1351(2004).8.S.Zhang,W.Fan,B.K.Minhas,A.Frauenglass,K.J.Malloy,and S.R.J.Brueck,Phys.Rev.Lett.94,037402(2005).9.A.Berrier,M.Mulot,M.Swillo,M.Qiu,L.Thylén,A.Talneau,and S.Anand,Phys.Rev.Lett.93,073902(2004).10.E.Schonbrun,M.Tinker,W.Park,and J.-B.Lee,IEEEPhoton.Technol.Lett.17,1196(2005).11.V .A.Podolskiy,A.K.Sarychev,and V .M.Shalaev,J.Nonlinear Opt.Phys.Mater.11,65(2002).12.V .A.Podolskiy,A.K.Sarychev,and V .M.Shalaev,Opt.Express 11,735(2003).13.Y.Svirko,N.Zheludev,and M.Osipov,Appl.Phys.Lett.78,498(2001).14.A.Taﬂove and S.Hagness,ComputationalElectrodynamics:the Finite-Difference Time-Domain Method (Artech,2000).15.D.R.Smith,S.Schultz,P .Markôs,and C.M.Soukoulis,Phys.Rev.B 65,195104(2002).Fig.3.(Color online)(a)Real and imaginary parts of the refractive index retrieved from simulations.(b)Real part of the refractive index retrieved from simulations (triangles)and experiments (circles).The inset in (b)is a magniﬁed view of the region of negative refraction;the dashed curve shows the quadratic least-squares ﬁt for the experimental data.3358OPTICS LETTERS /Vol.30,No.24/December 15,2005。

显微镜镜头设计专业英文翻译资料

CHINESE JOURNAL OF PHYSICS VOL.38,NO.2-I APRIL2000 High Voltage and High Current Density Objective LensA.S.A.AlamirDepartment of Physics,Assiut University,Assiut,Egypt(Received June29,1999)Iron-free objective focal properties have been computed as a function of the current density, which is the limiting factor.Practical lenses with of low aberration coefficients have beensuggested for use in high resolution and high voltage electron microscopes.PACS.41.80.-p–Beam optics.I.IntroductionA magnetic objective lens should have a small aberration coefficient to achieve high reso-lution and,if possible,a large space must be available around the specimen to allow for specimen manipulation.To do this,one should design a lens with the highest possible axial flux density and the smallest half width of the axial field distribution.The limiting factor for the axial flux distribution B z,of a given magnetic lens,is the current density¾that can be supported by the energizing coil.Hence,for a specific ratio(D2=D1)of the outer to inner diameter,and S=D M,the ratio of the axial thickness to the mean diameter,the actual size of the coil and hence of a lens of given shape,will be decided by the current density in the winding,since in electron optics the excitation NI is usually a given quantity[1].For better resolution,the required lens performance can be achieved only by the use of iron polepieces separated by an extremely small gap and bore,usually on the order of a millimeter[2].This in turn leads to difficulties with specimen manipulation[3]and in the extraction of X-rays and secondary electrons from the specimen.The resolution of both single and double polepiece lenses is approximately the same.Moreover,an improvement in the resolution may not be worthwhile in practice,for a current density¾greater than about105A/cm2[3,4].An iron-free coil offers new possibilities for overcoming these disadvantages.In principle,an iron-free objective lens provides a lower aberration coefficient at very much higher current density¾than is possible with an iron-polepieces lens[5].Open coils are relatively easy to make,but it has proven to be very difficult to achieve the necessary rotational symmetry in these small coils.As a result such lenses suffer from excessive astigmatism[6].It should be mentioned that pancake coils,as proposed by[7]for room temperature lenses,show a much better performance if constructed from superconductors[8].It is more practical to determine the optical properties and dimensions by choosing the value of¾that corresponds to the desired minimum aberration[9].One advantage of iron-free coils is their size reduction with respect to the iron circuit lenses. It is therefore desirable to describe some recent investigations of iron-free objective lenses that offer the possibility of developing electron optical instruments,both with and without the use of superconducting windings.139c°2000THE PHYSICAL SOCIETYOF THE REPUBLIC OF CHINA140HIGH VOLTAGE AND HIGH CURRENT ¢¢¢VOL.38II.The axial flux densityThe axial flux density B (z )of an iron-free coil Fig.1is given by [5]:B (z )=¹0NI 26664(S ¡z )ln R 2+µR 22+(z ¡S )2¶1=2R 1+µR 21+(z ¡S )2¶+(S +z )ln R 2+µR 22+(z +S )2¶1=2R 1+µR 21+(z ¡S )2¶37775;(1)where,¹0=4¼£10¡7Hm and 1=R 2¡R 1.R 1,R 2,S and z are in meters,NI is in ampereturns and B (z )is in teslas.Since¾A =NI;(2)where ¾is the current density and A =°1S is the cross-sectional area of the energizing coil,which is given by:A =°(R 2¡R 1)s =°1s;(3)where °is the packing factor (°=0:9,for copper tape windings),the axial flux densityB (z )takes theform:FIG.1.Iron-free rectangular cross-sections.With an inner radius R 1,outer radius R 2,and coil thicknessmean radius R M =(R 1+R 2)=2.VOL.38 A.S.A.ALAMIR141FIG.2.The variation of the spherical aberration coefficient C s of an iron-free coil with current density ¾(Z=0;V=1000KV).B(z)=¹0¾26664(S¡z)ln R2+µR22+(z¡S)2¶1=2R1+µR21+(z¡S)2¶+(S+z)lnR2+µR22+(z+S)2¶1=2R1+µR21+(z¡S)2¶37775:(4)peak value B0of the axial flux density can be expressed as:B0=¹0S226664ln R2+µR22+(S2)2¶1=2R1+µR21+(S)2¶1=237775¾:(5)Therefore,the maximum axial flux density B0of an iron-free coil varies with¾,in other words the aberrations of the iron-free coils vary as¾¡1.III.Focal propertiesFor an objective lens,spherical and chromatic aberrations have the largest effect.These aberrations can be reduced by reducing the focal length.In pratice,the most suitable objective lenses for high resolution work are those having the shortest possible focal lengths.The results for the focal properties of such lenses are putations have been carried out for an electron beam of1MV entering a paraolel to the optical axis lens,with D2=D1=38:7and different values of S=D M.The beam intersects the optical axis at the center of the coil(at the specimen position,i.e z=0).142HIGH VOLTAGE AND HIGH CURRENT¢¢¢VOL.38FIG.3.The variations of the chromatic aberration coefficient C s of an iron-free coil with current density ¾(Z=0;V=1000KV).First,we examine spherical aberration.Fig.2shows a log-log plot of the spherical aberration coefficients for such lenses,as a function of the current density¾.This kind with plot shows the variation of above coefficients more clear than a linear plot can.The lens with S=D M=0:3has the smallest C s value.Fig.3shows that the S=D M=1lens has smallest value for the chromatic aberration coefficient C c.Calculations of the objective focal length f0show that the S=D M=1:4lens has the shortest objective focal length f0.It can be seen that the focal properties of the iron-free lenses improve with increasing¾,there is no optimum value for¾at which C s or C c is a minimum.The improvement of a lens is therefore largely limited by the technology and engineering of the high current density windings.The shape represented by the ratio D2=D1,was studied for S=D M=0:3.Calculations were made for lenses of D2=D1=19,38.7,and999.The results are shown in Fig.4,which gives the spherical aberration coefficient as a function of the current density¾.The spherical aberration coefficient C s gets smaller as the ratio D2=D1gets larger for a given S=D M.IV.Practical lensThe axial field distribution of a coil with D2=D1=54:5cm/2.7cm=19and S=D M=0:3operating at1MV is shown in Fig.5this is a typical working lens for a million-volt electron microscope.This lens is used as a condenser-objective at the current density¾=20000A/cm2(the value of¾=20000A/cm2 has been adopted as the point beyond which the use of a superconducting winding can not be avoided).Fig.6shows that both the spherical and chromatic aberration coefficients decrease with increasing current density¾.The characteristics of this lens are shown in Fig.7,for different current density values¾.As¾increases the,D M of the1MV lens decreases in the same manner as C s and S.At¾=20000A/cm2, the lens size is suitable,the maximum field density is B0=2:46Tesla,and the resolution power is ±(=0:7(Cs¸3)1=4),¸being the electron wave length)=1.35A0.VOL.38 A.S.A.ALAMIR143FIG.4.The spherical aberration coefficient for an iron-free lens with D1=D2==999,38.7,19and S=D M=0:3as a function of the current density.FIG.5.The axial flux density of an iron-free condenser-objective lens.(D2=D1=19;S=D M=0:3).144HIGH VOLTAGE AND HIGH CURRENT¢¢¢VOL.38FIG.6.Objective focal properties of a1MV condenser-objective iron-free lens(D2=D1=19, S=D M=0:3)as a function of the current density¾.At high current densitv values(103<¾<107),a region favourable for iron-free lenses,the resolution is of the order0.75-0.55A0,but the corresponding out sick diameter of the lens is impracticaly small.The mechanical design of such lenses becomes easier as the accelerating voltage increases.Practical applications for such lenses have only been considered for very high beam voltages»3MV[10].For the same value of¾(20000A/cm2),the lens in Fig.5is used as a condenser-objective lens at an accelerating voltage of1.4MV.This lens has the following dimensions:D2=58:5mm,D1=3 mm(to permit the specimen holder to be introduced on the electron source side),S=D M=0:3,with a maximum field density of B0=2:64Tesla.The calculated focal properties of this lens are f0=8:3mm, C s=2:2mm,C c=4:9mm with a resolution power of±=0:1nm.These excellent aberration properties are accompanied by a considerable reduction in lens size compared with conventional lenses.The designs shown here are not intended to show the limits of performance of such lenses,but to indicate that good electron optical properties,comparable with those of the best conventional lenses,may be achieved even at modest flux densities and with simple construction.VOL.38 A.S.A.ALAMIR145FIG.7.The mean diameter D M,the thickness of the coil S,the spherical aberration coefficient C s together with the resolution power±,as function of the current density¾(D2=D1=19).V.ConclutionThe focal properties of iron-free lenses have been improved continuously by increasing the current density.There is no limit to lens improvements except that set by the maximum permissible current density in the winding.The chief benefits of such lenses are likely to be realized in high voltage,high resolution electron microscopes using superconducting windings.References[1]I.S.Al-Nakeshili,Ph.D.thsis,Univ.of Aston in Birrningham,U.K.(1986).[2]T.Mulvey,Magnetic electron priprrties,ed(Hawkes,P.W.Springer.1982),Ch.5.[3]I.S.Al-Nakeshili,S.A.Juma,and T.Mulvey,in Electron Microscopy1eds.Roshlich and Dszabo(Budapest Program Cornmmittee of8th Eur.Cong.on Elect.Micros.)21,(1984b).[4]I.S.Al-Nakeshili,S.A.Juma,and T.Mulvey,in Electron Microscopy and nalysis ed.P.Diog,Inst.Phys.Conf.Ser.68,475(1984a).[5] A.S.A.Alamir,J.phys.D.Appl.Phys.25,1039(1992).[6]P.W.Hawkes and U.V aldre,J.Phys.E309(1977).[7]T.Mulvey and C.D.Newman,in proc.5th Eur.Cong.on Electron Microscopy,Manchester,116(1969).[8] D.Genotel,C.Severin,and berrigue,J.microscopy6,933(1967).[9] A.S.A.Alamir,J.of Microscopy179,137(1994).[10]G.Lefranc,E.Knapek,and I.Dietrich,Ultramicroscopy10,111(1982).。

蓝星硅胶

Bluestar Silicones. Delivering Your Potential.Bluestar Silicones materials are used for photovoltaic module applications to improve their reliability and durability due to their unique features. ESA products, Electronic Silicone Adhesives, are two components silicone elastomers which cure at room temperature (RTV-2) by polyaddition reaction. The curing can be accelerated by heating. After curing, gels or elastic materials are available from the ESA range.ESA Potting materials have excellent weather resistance and give an excellent protection against moisture.These properties associated with high electrical insulation performances, fire resistance (UL approvals), thermalconductivity, wide temperature range stability (-40°C to +150°C) are key parameters for a long term operation of the junction box. Suitable for automated dispensing, ESA potting agents are ideal for mass production. A quick curing version is also available, which allows to turn the panel around 15 minutes after having applied the product.ESA Encapsulation materials have an excellent opticaltransmittance over a wide light spectrum. This high transparency combined with outstanding UV stability, high temperature and electrical stability, and protection against moisture make ESA encapsulants excellent candidates to improve long term cell efficiency.In addition, ESA encapsulation agents also provide excellent adhesion properties.蓝星有机硅材料可应用于光伏模组，提高产品可靠性和持久性。

相关主题

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

a rXiv:as tr o-ph/36169v19J un23An AGN Sample with High X-ray-to-optical Flux Ratio from RASS II.Optical Emission Line Properties of Seyfert 1Type AGN D.W.Xu 1,2,Stefanie Komossa 2,J.Y.Wei 1,Y.Qian 3and X.Z.Zheng 1ABSTRACT This work studies the optical emission line properties of a sample of 155low-redshift bright X-ray selected ROSAT Seyfert 1type AGN for which ade-quate signal-to-noise ratio spectroscopic observations are available.We measured emission line properties by performing multi-component ﬁts to the emission line proﬁles,covering the eﬀect of blended iron emission.We also obtained contin-uum parameters,including 250eV X-ray luminosities derived from the ROSAT database.In addition,the measured properties are gathered for a correlation analysis,which conﬁrms the well-known relations between the strengths of Fe II,[O III]emission and the X-ray slope.We also detect striking correlations between H βredshift (or blueshift),ﬂux ratios of Fe II to H βbroad component and [O III]to H βnarrow component.These trends are most likely driven by the Eddington ratio.Subject headings:Galaxies:Seyfert –Quasars:emission lines –X-rays:galaxies 1.IntroductionOptical spectra of Active Galactic Nuclei (AGN)exhibit an extremely wide variety of properties.The emission-line regions of AGN have proven to be among the most complex of all astrophysical environments (Corbin &Boroson 1996).AGN have also been known to emit a substantial fraction of their luminosity as X-rays.Multi-wavelength observations of well-deﬁned source samples are eﬀective in understanding the physical processes in AGN.In the last decade,several correlations between optical emission line properties and X-ray properties were noted(Boroson&Green1992;Lawrence et al.1997;Grupe et al.1999; Vaughan et al.2001):for instance,the strong correlations between optical Fe II,[O III]λ5007 line strengths,velocity width of Hβand the slope of soft X-ray continuum(αX).These correlations received great interest previously and were expected to give important insight into the AGN phenomenon.Still,however,their interpretation remained unclear.It is therefore of great importance to test whether these correlations are fundamental properties or subtle selection eﬀects,and search for new ones.Clearly,a large and homogeneous X-ray selected sample would be advantageous in addressing these issues.We present such a sample here.X-ray AGN samples are also of great interest for a number of other issues.AGN of dif-ferent types are the major contributors to the extragalactic soft and hard X-ray background (XRB).The deﬁnitions of statistically signiﬁcant AGN samples using X-ray data are key to test AGN number-ﬂux relations,luminosity functions and cosmological evolution.In the course of the ROSAT All Sky Survey(RASS)(Voges et al.1996,1999),many new AGN have been identiﬁed by diﬀerent teams,conﬁrming that X-ray surveys are very eﬃcient inﬁnding new AGN.Schwope(2000)performed an unbiased survey of all bright,CR>0.2s−1,high galactic latitude sources in the RASS without applying other selection criteria.Wei et al. (1999,Paper I)identiﬁed a sample with high X-ray to opticalﬂux ratio.Appenzeller et al. (1998)and Zickgraf et al.(1997)presented a catalog of sources in selected areas down to the RASS limit.Thomas et al.(1998)drew a high galactic latitude sample from the RASS with soft PSPC spectra(HR1<0.0),the corresponding sample of point-like X-ray sources with relatively hard X-ray spectra(HR1>0.5)was presented by Fischer et al.(1998).Bade et al. (1995,1998)published a catalog of northern AGN in the RASS based on their Schmidt plate survey.These authors presented new AGN,but they did not use their samples to address correlations issues.This will be done with the present sample.In Paper I we described and presented the optical identiﬁcation of a sample of165X-ray sources with high X-ray to opticalﬂux ratio(f X/f opt)discovered in the RASS.About73%of the sources were identiﬁed as AGN,including115emission line AGN(QSOs and Seyferts) as well as2BL Lac objects and4BL Lac candidates.In this paper we investigate the optical emission line properties of the emission line AGN that were identiﬁed as main optical counterparts of the sample and discuss their connection with X-ray properties.Not included in the following discussion are the BL Lac objects.The initial identiﬁcation program excluded known X-ray sources that have counterparts in the SIMBAD,NED and AGN catalogs.Motivated by the need of larger and better samples,we have cross-referenced the RASS bright source catalog with the NED and AGNcatalogs.Weﬁnd that40known emission line AGN meet our selection criteria.4In order to keep consistent emission line properties measurements,new optical spectra have been acquired for the40additional sources.These data,combined with the previous optical identiﬁcations,provide a large,bright and(f X/f opt)limited sample of emission line AGN in the ROSAT X-ray band.The relatively complete sample is the largest X-ray selected AGN sample with intense optical investigation so far.As described in Paper I,our classiﬁcations and identiﬁcations were based on low reso-lution spectra obtained with a2.16m telescope at Xinglong station,National Astronomical Observatories of China(NAOC).These spectra were exposed to reach a S/N suitable for a reliable classiﬁcation.The quality of the majority spectra is suﬃcient to measure the properties of the emission lines,such as the line widths and line strengths.For spectra with inadequate S/N,new low resolution(∼10˚A FWHM)optical spectroscopy was performed using the2.16m telescope at NAOC.All objects in our emission line AGN subsample are found to be Seyfert1type AGN. Throughout this paper Seyfert1galaxies and QSOs will be discussed jointly,since these two classes are distinguished only by a certain luminosity level according to our classiﬁcation criterion.We do not divide the Seyfert1class into subclasses such as Seyfert1.5-1.9or NLS1galaxies(as deﬁned by V´e ron-Cetty&V´e ron(2000),Osterbrock&Pogge(1985)), since the deﬁnitions of Seyfert classiﬁcations depend on the resolution of the spectra used and the noise in the spectra(Grupe et al.1999;Goodrich1989a,b).The paper is organized as follows.Detailed optical measurements are given in Sect.2. The statistical properties are investigated in Sect.3.Several diagnostically important cor-relations that exist between emission line and continuum properties are studied.Sect.4 discusses the implications of the results,followed by a brief summary of the main conclu-sions of the paper.Throughout this paper,a Hubble constant of H0=50km s−1Mpc−1and a deceleration parameter of q0=0are assumed and all measured parameters are quoted for the rest frame of the source.2.Observations and Optical Measurements2.1.New Optical ObservationsThe known sources as well as sources without high quality observations in the identiﬁ-cation campaign were investigated during several observing runs performed from November 1998through December2000.The low resolution spectra were taken with the NAOC2.16m telescope and the OMR spectrograph,using a Tektronix1024×1024CCD as detector.The grating of300g mm−1was employed in order to get large wavelength coverage.All observa-tions were made through a2.3′′slit that produced a resolution of10to11˚A as measured from the comparison spectra.This set-up provided similar wavelength coverage(3800˚A–8200˚A) and resolution to the identiﬁcation data.Exposure time was generally between1200s and 3600s depending on the brightness of the object.For a few objects,multiple exposures were performed in order to get a higher S/N spectrum.The exposures were combined prior to extraction where possible in order to help remove cosmic ray contamination.In cases when the target source moved across the CCD chip between exposures,the data were extracted separately from each frame and then combined.The raw data were reduced following standard procedures using IRAF.The CCD re-ductions included bias subtraction,ﬂatﬁeld correction and cosmic-ray removal.Wavelength calibration was carried out using helium-neon-argon lamps taken at the beginning and end of each exposure.The resulting wavelength accuracy is better than1˚A.Theﬂux calibration was derived with2to3observations of KPNO standard stars(Massey&Strobel1988)per night.2.2.Fe II SubtractionIn many of the spectra there is a clear contribution from blends of Fe II line emission on both the blue and red sides of the Hβ-[O III]complex.These blends contaminate strong lines such as[O III]λλ4959,5007,and may alter theﬂux and width of Hβ+[O III]λλ4959,5007.In order to reliably measure line parameters and to determine the strength of the Fe II emission, we have carefully removed the Fe II multiplets following the method described by Boroson &Green(1992),which relies on an Fe II template.The template used in the present work is the same as that of Boroson&Green(1992),namely the Fe II lines of I Zw1,a bright NLS1widely known for the strong and narrow permitted Fe II emission(Phillips1978;Oke &Lauer1979).The observed spectra were wavelength-shifted to the rest frame accordingto the redshift.5The whole template was broadened to the FWHM of the broad Hβline by convolving with a Gaussian and scaled to match the line intensities.The best match was then searched for in the two-dimensional parameter space of line width and line strength.From each object the best-ﬁt Fe II spectrum was then subtracted.A successful Fe II subtraction showed aﬂat continuum between the Hγand Hβand between5100–5400˚A(which covers the Fe II multiplets48,49).The Fe IIﬂux was measured between the rest wavelength4434˚A and 4684˚A as in Boroson&Green(1992).2.3.Other Line MeasurementsThe characteristic property of Seyfert1type AGN is the presence of broad emission lines.The line widths and their distributions provide important information on masses of the central black holes and mass distributions.The broad Balmer lines in AGN exhibit a wide variety of proﬁle shapes and a large range in width(Osterbrock&Shuder1982;de Robertis 1985;Creshaw1986;Stripe1991;Miller et al.1992;V´e ron-Cetty,V´e ron&Gon¸c alves2001) and they are often strongly asymmetric(Corbin1995).In many cases Hβis a mixture of broad and narrow components.Diﬀerences in the relative strengths of these components account for much of the diversity of broad line proﬁles(Francis et al.1992;Wills et al.1993; Brotherton et al.1994;Corbin1995,1997;V´e ron-Cetty,V´e ron&Gon¸c alves2001).The Fe II subtracted spectra were used to measure the non-Fe II line properties.In order to isolate the broad Hβcomponent in all spectra,we have assumed that the emission line proﬁles can be represented by a single or a combination of Gaussian proﬁles.V´e ron-Cetty,V´e ron&Gon¸c alves(2001)claimed that the broad emission lines in NLS1galaxies were betterﬁtted with Lorentzian proﬁles than with Gaussian proﬁles.However,as noted in Evans(1988),the choice of Gaussian or Lorentzian proﬁles as representatives of the observed emission lines may bear no physical meaning.We performed a multiple Gaussian ﬁt in the present work for its simplicity and a direct comparison with the measurements of previous studies(e.g.Boroson&Green(1992);Grupe et al.(1999);Vaughan et al. (2001)).We adopted the method described by Rodr’iguez-Ardila et al.(2000b)and used the IRAF package SPECFIT6to measure blended lines.As aﬁrst step we tried toﬁt the emission lines with a single Gaussian component.It worked well for most forbidden lines, e.g.,[O III]λ5007.However,this simplest representation could notﬁt adequately the wingsof Hβ,although its core was nicelyﬁtted in most of targets.In such cases,we then included one narrow component and one broad component to describe adequately the observed proﬁle. (Note that when Hβmeasurements were taken from the literature,many of them refer to the whole line.)For each assumed component,aﬁrst guess of the central wavelength,the totalﬂux,and width of that component were speciﬁed.There were two parameters for each continuum component,i.e.,theﬂux and the slope.Initially,we constructed a narrow component with a width determined fromﬁtting the[O III]lines.In some spectra such a guess failed to give a goodﬁt and needed an additional component.We then left the width of the narrow component as a free parameter.It led to a niceﬁtting result by checking the residual,i.e.,the narrow component could be well isolated from the broad component. For Hβlines with asymmetric proﬁle,the two Gaussian components are not stationary in wavelength.The velocity shift between the broad and narrow components is deﬁned as the shift of the broad component relative to the narrow component in units of km s−1(see also Zheng et al2002).As an illustration,we show the decomposition in Figure1.The observed proﬁle is represented by a solid line,the totalﬁt by a dashed line,the individual Gaussian components by a dot-dashed line and the diﬀerences between the data and theﬁt (the residual)by the lower dotted line.The broad component is referred as Hβb,and the narrow component as Hβn.The FWHM Hβb is what we consider as representative of the Broad Line Region(BLR).The instrumental resolution was determined from the FWHMs of night sky spectra taken with each of the exposures and tested by comparison-lamp spectra.All quoted line widths were corrected for the instrumental resolution.The uncertainty of Hβvelocity shift measurement is within150km s−1.To measure lineﬂuxes and equivalent widths(EW),power-law con-tinua wereﬁtted and subtracted from underneath the lines and the remaining lineﬂux was integrated.For most objects,the uncertainty ofﬂux measurement of emission lines is about 10%to15%.2.4.Continuum MeasurementsThe continuum level at the position of Hβλ4861was measured from the Fe II subtracted spectra.All equivalent widths measurements in this paper refer to the continuum at that point to allow direct comparison with the measurements for other samples(Boroson&Green 1992;Grupe et al.1999;Vaughan et al.2001).The optical indexαopt was calculated using the continuumﬂux density at4000˚A and7000˚A in the rest frame.For the X-ray analysis,a single power law description was employed.This application has proven to be a fairly good approximation for AGN in previous studies(e.g.Fiore etal.1994,Brinkmann&Siebert1994,Schartel et al.1996,Grupe et al.1998).Because of the limited signal-to-noise ratio of the RASS spectra we assumed that the absorption comes from our Galaxy only.The assumption usually improves the reliability of the estimation of spectral index because of the reduced number of free parameters.The X-ray spectral slope αX(Fν∝ν−α)was estimated using the ROSAT hardness ratios HR1and HR2,which are deﬁned as(Voges et al.1999):B−AHR1=D+CHere,A,B,C and D denote the count rate in the energy range0.1–0.4keV,0.5–2.0keV, 0.5–0.9keV and0.9–2.0keV,respectively.3.Analysis3.1.General Sample PropertiesThe full optical dataset was used to deﬁne the statistical properties of the sample and explore the correlations between various observed parameters.According to Paper I,115 sources(about73%of the total)were identiﬁed as new Seyfert1s and QSOs,together with 40known emission line AGN that meet our sample selection criteria,the AGN subsample comprises49“ultrasoft”(αX>1.7)sources and106“normal”objects with mean<αX>= 1.43.In the catalog in Paper I we listed the absolute magnitude M B and redshift z.The distributions of the M B values and redshift are plotted in Figure2.As shown by these ﬁgures,the sample is dominated by moderate luminosity objects(M B≈−23±2)with an average redshift<z>=0.2.Table1lists the derived parameters.The columns list the following information:(2) redshift;(3)FWHM of broad Hβ;(4)FWHM of narrow Hβ;(5)FWHM of[O III]λ5007;(6),(7)and(8)the local equivalent widths of Hβbroad component,Fe II and[O III]λ5007;(9)and(10)ratio ofﬂuxes of[O III]λ5007to broad and narrow Hβ;(11)ratio ofﬂuxes of Fe II to broad Hβ;(12)velocity shift between Hβbroad and narrow components,where a positive velocity corresponds to a redshifted broad component relative to narrow component;(13)and(14)Hβbroad and narrow components velocity shift with respect to the systemic frame,where a positive velocity indicates a redward shift with respect to systemic;(15)and (16)spectral indices deﬁned above;(17)the monochromatic250eV luminosity.The distribution of the broad Hβline width of the objects in our emission line AGN subsample shows a signiﬁcantly smaller fraction(3%)of objects with FWHM<2000km s−1compared to another X-ray selected sample(18%)(Appenzeller et al.2000).However,the FWHM measurements in Appenzeller et al.(2000)refer to the full line proﬁle and the widths of the broad components may have been underestimated.Therefore,the real diﬀerence should be smaller.Five out of155objects in our sample are NLS1galaxies without detectable broad Balmer line components of FWHM>2000km s−1but with strong Fe II emission, which agrees within the error limits with that of Appenzeller et al.(2000)(about2%).The distribution of the FWHM of the broad component of Hβin the sample is displayed in Figure3.The mean value of4350km s−1is similar to the hard sample of Grupe et al. (1999).3.2.Distribution of Velocity ShiftsThe velocity shift distribution of Hβb with respect to[O III]λ5007is shown in Figure4a. Positive velocity corresponds to a redward Hβwith respect to systemic,while a negative velocity represents a blueshift.The peak of this distribution is near zero,but has a mean redshift of78km s−1with standard deviation of305km s−1.This shift is in good agreement with the previous studies(Gaskell1982;Tytler&Fan1992;Boroson&Green1992;Laor et al.1995;Corbin&Boroson1996),i.e.,Balmer emission lines gives the same redshift to within100km s−1of narrow forbidden emission(e.g.[O III]λ5007)in low redshift(z<1) QSOs and Seyfert galaxies.In contrast,a systematic mean redward shift of520km s−1was found for a high redshift(2.0 z 2.5)QSOs sample(McIntosh et al.1999).McIntosh et al.(1999)proposed this observed trend of increased Balmer redshift with increased systemic redshift represents a luminosity dependency.For comparison,we also present the Hβn–[O III]λ5007shift in Figure4b.The mean of the distribution is8km s−1with a standard deviation of176km s−1.We can see from theﬁgures that the dispersion of the Hβn–[O III]λ5007shift is signiﬁcantly narrower than the Hβb–[O III]λ5007shift,which is expected by the diﬀerent emitting regions between Hβbroad component and narrow component,as well as[O III]λ5007.In a similar manner to the Hβb–[O III]λ5007shift,Figure4c illustrates the velocity diﬀerences between the broad and narrow components of Hβ.The redshift(or blueshift)is deﬁned as the shift of the broad component relative to the narrow component in units of km s−1.Positive velocities refer to redshifts with respect to the narrow component velocities, whereas negative velocities indicate blueshifts.We emphasis that both the Hβredshift(or blueshift)in the present work and the asymmetry parameter in Boroson&Green(1992) are measures for line proﬁle,but characterized diﬀerently.The latter is a measure of the shift between the centroids at1/4and3/4maximum.The mean redshift of the distributionis found to be70km s−1with a standard deviation of357km s−1.Correlation analyses involving the line proﬁles of Hβare investigated in section3.3.3.3.Correlations AnalysisIn this subsection,we explore whether the various emission-line and continuum prop-erties correlate with one another.For this purpose,we calculated the Spearman rank-order correlation matrix(Press et al.1992),along with its signiﬁcance matrix for measured prop-erties.The complete correlation coeﬃcient matrix is shown in Table2.The number of parameter pairs included in the trials ranges from86to149.Spectra with S/N<10were excluded from the analyses including optical properties.The probability of the null correla-tion,Ps,for a sample with corresponding correlation coeﬃcient Rs is also given in Table2for entries with Ps<0.01.A set of12diﬀerent properties results in12×(11/2)=66correlation coeﬃcients;therefore,at this level of signiﬁcance,we would expect 1spurious events.Among66trials,31correlations(both positive and negative)are found with two-sided probabilities Ps<0.01.Four are due to the dependent parameters,e.g.,relative strength of Fe II to Hβand Fe II EW;12are degenerate correlations,i.e.,diﬀerent measures of the same property(e.g.,[O III]EW,[O III]/Hβb and[O III]/Hβn)all correlate with another property (e.g.,Fe II EW);and therefore15are independent correlations at the 99%conﬁdence level.The well-known anti-correlation between the X-ray spectral slopeαX and the FWHM of Hβ(Boller et al.1996;Laor et al.1997;Grupe et al.1999)is not prominent in our sample (Rs=−0.20,Ps=0.05)as is the case in the Vaughan et al.(2001)sample(Rs=−0.31, Ps=0.03).Vaughan et al.(2001)suggested that the relation between Hβwidth andαX is not a linear correlation,but probably resulted from a“zone of avoidance”(Komossa et al.2001),i.e.,broad line objects always tend to showﬂat X-ray spectra,whereas there is a very large scatter in the X-ray spectral steepness of NLS1galaxies,with several asﬂat as normal Seyfert1s(Xu et al.1999).The correlation is more pronounced among the AGN with higher luminosity as in the samples of Grupe et al.(1999)and Vaughan et al.(2001). For objects withνL250eV>1044.3erg s−1the signiﬁcance becomes Rs=−0.45(Ps=0.007). The correlation betweenαX and Hβb is illustrated in Figure5.The anti-correlation between the width of Hβand Fe II/Hβ(Wills1982;Boroson &Green1992;Wang,Brinkmann,&Bergeron1996;Rodr’iguez-Ardila et al.2000a)is strong(Rs=−0.59,Ps<10−4)in the present data whereas it is only weak(Rs=−0.31, Ps=0.002)if FWHM Hβis compared directly with EW Fe II.Instead,there is a strongcorrelation(Rs=0.56,Ps<10−4)between FWHM Hβand EW Hβ.The lack of correla-tion between the line width and Fe II strength(when measured independently with Hβ) in Grupe et al.(1999),Vaughan et al.(2001)and the present work has conﬁrmed that the anti-correlation arises because Hβgets weaker as the lines get narrower(Osterbrock1977; Gaskell1985;Goodrich1989b;Gaskell2000).In addition to our conﬁrmation of well documented correlations between diﬀerent AGN properties,we report on three newly discovered correlations involving the Hβredshift(or blueshift),ﬂux ratios of Fe II to Hβbroad component(Fe II/Hβb)and[O III]to Hβnarrow component([O III]/Hβn).The correlations covering[O III]/Hβn have never been investi-gated by other authors so far.Weﬁnd the relative strength of Fe II to Hβb(Fe II/Hβb) signiﬁcantly correlated to both the Hβredshift7(Rs=−0.64,Ps<10−4)and the relative strength of[O III]to Hβn([O III]/Hβn,Rs=−0.60,Ps<10−4).A correlation test was also applied between Hβredshift and[O III]/Hβn.The correlation is prominent in our sample(Rs=−0.38,Ps<3×10−4).Figure6shows the correlations.There is a trend that strong Fe II/Hβb–weak[O III]/Hβn objects tend to have blueshifts in Hβwhile strong [O III]/Hβn–weak Fe II/Hβb objects tend to have redshifts in Hβ.These strong correla-tions between Fe II/Hβb,Hβredshift and[O III]/Hβn must reﬂect some physical connection between broad and narrow line emitting regions.4.DiscussionOne key to understand the central engines of AGN lies in examining their local en-vironment.The standard paradigm proposes that the surrounding gas is photoionized in physically distinct regions by radiation emerging from the central power source(Osterbrock 1989).However,the segregation of the ionized gas into broad-line region(BLR)and narrow-line region(NLR),as well as the details of the gas kinematics are still far from clear.Optical spectroscopy of the ionized gas around galactic nuclei provides strong constraints on the excitation mechanisms.The following discussion addresses three key points:(1)how do the present results compare to previous work;(2)which new correlations do weﬁnd and how can we understand them;and(3)which future observations can we perform to distinguish between diﬀerent suggested scenarios.A number of consistent correlations among observational parameters have been searched in order to understand the basic properties underlying the observed spectra.In particular, Boroson&Green(1992)made a landmark study of the optical emission-line properties and continuum properties(radio through X-ray)of87low redshift PG quasars.A principal component analysis revealed“eigenvector1”(EV1)links stronger Fe II emission,weaker [O III]emission from the NLR,and narrower Hβ(BLR)with stronger line blue asymmetry. More recently,Laor et al.(1997)found these optical properties also go along with steeper soft X-ray spectra and claimed the soft X-ray slope as a related part of EV1.We conﬁrm these trends and present in addition three newly discovered correlations involving the Hβredshift,Fe II/Hβb and[O III]/Hβn.Potentially,EV1represents a fundamental physical driver that control the energy pro-ducing and radiation emitting processes.The two leading interpretations by far are that EV1 is driven by(1)the Eddington ratio L/L Edd(Boroson&Green1992)and(2)Orientation eﬀect.Boroson&Green(1992)argued strongly that viewing angle is unlikely to drive EV1, by assuming[O III]emission is isotropic,originating from radii large enough to be free from orientation dependent obscuration.The isotropy of[O III]emission has been questioned by the studies of radio-loud AGN(Hes,Barthel&Fosbury1993;Baker1997).However,a recent study of radio-quiet quasars(Kuraszkiewicz2000)showed a signiﬁcant correlation between EV1and orientation independent[O II]emission,which implied that EV1is not driven by orientation.Moreover,the correlation between[O II]and[O III]emission indicated[O III] emission is not dependent on orientation.The most promising interpretation at present is that EV1is mostly governed by L/L Edd (Boroson&Green1992).This suggestion was based on the notion that the vertical thick-ness of the accretion disk,driven by the Eddington ratio,controls the line strengths and continuum parameters.The striking correlations between the Hβredshift,Fe II/Hβb and[O III]/Hβn found in the present work give us linkages of the gas kinematics and ionization between BLR and NLR.The question raised is what is the physical process behind the correlations?Can both the new and previous correlations be explained within one single scenario?Indeed,the L/L Edd interpretation provides plausible explanations for the observed trends.One of the two general scenarios in AGN to explain asymmetric proﬁle is in terms of an outﬂowing component in the BLR with a change in obscuration by a central disk of clouds on the receding side.Accreting systems in high L/L Edd AGN will drive relatively thick outﬂows due to their larger photon luminosities per unit gravitational mass.As the velocity of theoutﬂow increases,the Hβdevelops an increasing excess on the blue wing.The corresponding blue Hβb velocity shift in comparison with[O III]can be also well predicted because both the line asymmetry and the shift of the line centroids are eﬀects of the same process.The link between BLR and NLR in terms of density is less straight forward to predict. E.g., due to the strong outﬂow,the NLR might be replaced by denser clouds.Given a typical radial distribution of NLR clouds,[O III]/Hβn peaks around densities of log n=2–4(e.g., Komossa&Schulz1997).High-density NLR clouds would therefore lead to a suppression of[O III]strength.The same is true for the other limit,a low-density NLR.Some authors favored a low-density BLR of NLS1galaxies(see,e.g.,the discussion in Rodriguez-Pascual et al.1997and Komossa&Mathur2001),which may indicate a low-density NLR as well, if both regions are coupled.The best way to measure directly the density of the NLR of NLS1s in the future is to employ the density-sensitive line ratios[O II]λ3729/[O II]λ3726or [S II]λ6716/[S II]λ6731.These ratios are presently generally not reported in the literature. Their measurements requires high S/N spectroscopy and/or resolution to detect and resolve these lines.8More indirectly,other line-ratios will also change in dependence of density and thus allow a density determination.For instance,a higher-density NLR would strongly boost the[O I]λ6300line(Komossa&Schulz1997).Although it is more diﬃcult to illustrate the direct connection between strong Fe II emission and large L/L Edd,some suggestions have been proposed.Pounds et al.(1995) suggested the X-ray spectrum becomes steeper in high L/L Edd AGN.If the EUV–X-ray spectrum plays an important role in the formation and conﬁnement of the BLR clouds(e.g., Krolik,McKee&Tarter1981),a steep X-ray spectrum coupled to aﬂatter EUV spectrum will lead to a thicker BLR(e.g.,Komossa&Meerschweinchen2000),and thus stronger Fe II emission if the the low-excitation part of the BLR is mechanically heated(Joly1987). Increased metal abundances in more extreme NLS1galaxies(Mathur2000)would enhance these trends,i.e.lead to thicker BLRs(Komossa et al.2001).Supersolar iron abundance may additionally boost the strength of Fe II.In another model by Kwan et al.(1995),Fe II line emission is produced in an accretion disk.The AGN with higher L/L Edd might simply have more mass in the accretion disk to produce stronger Fe II emission by postulating collisional excitation(Netzer&Wills1983;Wills,Netzer&Wills1985)as the origin of the Fe II emission in general.The strong correlations of properties linking dynamics(line widths),kinematics(line。