Improving the accuracy of aerosol extinction coefficient inversion

This paper considers the relationship between the accuracy of aerosol extinction inversion and the boundary value, and derives a theoretical high-accuracy aerosol extinction coefficient inversion. Aerosol extinction coefficient profiles depend on the boundary value. The relationship function of the differential extinction coefficient and differential boundary value is expressed by a maximum value. The smaller the differential boundary value, the smaller the differential extinction coefficient. The clean atmosphere layer is easily found from the lidar range-corrected signal, and the extinction coefficient of the clean atmosphere layer can be obtained using the slope method. By relating the extinction coefficient of the clean atmosphere layer to the extinction coefficient profiles at different boundary values, an accurate aerosol extinction coefficient profile can be obtained.     

Clear-sky monochromatic extinction coefficient and the transparency in Bahrain

Summary With the aim of developing a photometric observatory in Bahrain, we first started the analysis of Bahrain's sky. The extinction coefficient in magnitude scale (k) and the transparency of clear atmosphere (T) for Bahrain's sky have been deduced seasonally from the solar-spectrum intensity measurements in the wavelength range from 375 to 800 nm. A comparison of the calculated values for the (island) climate of Bahrain with those of the (desert) climate of Egypt is also presented. We conclude that the winter season is the best time for photometric observations in Bahrain. Empirical equations have been established, to show the relation between the transparency and the extinction coefficient with the wavelength for each season.     

Photoelectron spectroscopy in the energy region 30 to 800 eV using synchrotron radiation

With the advent of synchrotron radiation, the photoemission techniques were extended to a continuous range of excitation energies in the far ultraviolet and soft x-ray regions, adding tremendously to the usefulness of photoemission as a probe of the electronic structure of materials. In this paper, we discuss the application of photoelectron spectroscopy using synchrotron radiation to the studies of oxygen chemisorption/oxidation of Si surfaces, metal overlayers on III-V semiconductor surfaces, chemisorption on transition metal surfaces, and the surface electronic structure of CuNi alloys.     

The opacity coefficient method—nongray determination of inhomogeneous atmospheric extinction

The computation of radiation transmittance in nongray, inhomogeneous atmospheric models is frequently complicated by complex bands of line spectra which range in value over many orders of magnitudes and depend strongly on either or both of pressure and temperature. We present here a new opacity sampling technique which is shown to determine correctly the wavelength-averaged extinction due to path-dependent realizations of banded line spectra. The technique is easy to implement computationally and is applicable to a wide variety of atmospheric problems in which frequent iteration of the radiative transfer model is required. We consider two such instances: modeling of solar flux attenuation for use in a time-dependent planetary ionosphere model and retrieval from nadir measurements of backscattered solar irradiance. The power of the new method lies in its straightforward analytical treatment of both atmospheric inhomogeneity and spectral complexity. It is thus relevant for both retrieval and radiative transfer modeling purposes.     

Contribution of quantum molecular flexibility to the second virial coefficient of water vapor

The contribution of essentially quantum internal molecular motions to the second virial coefficient B2 of water vapor is analyzed in the framework of the path integral approach. A general purpose ab initio polarizable force field QMPFF2 or a nonpolarizable three-site water model are used with oscillator and Morse valence potentials. It is demonstrated that the contribution may be significant but depends strongly on the form of the intramolecular potential. In the case of the more realistic stretching Morse potential, inclusion of quantum molecular flexibility into the simulation reduces the virial coefficient by 20%-40%. Also, the internal modes make a contribution to the difference in the virial coefficient for light and heavy water, which is opposite to that of the intermolecular motions, so that the net effect can even change the sign at higher temperatures.     

碳纳米管对信息激光的消光系数测试研究

消光系数是表示烟幕干扰材料消光性能的重要参数,研究测试了三种不同尺寸的碳纳米管对1.06μm激光的消光系数。利用室内大型烟箱,根据Lambert-Beer定律,通过测量激光透过率和烟幕质量浓度,得到了不同时刻的碳纳米管烟幕对激光的消光系数。结果表明消光系数是一个变量,随碳纳米管材料的时空变化而变化。三种尺寸的碳纳米管对1.06μm激光的平均消光系数分别为1.3568 m2/g、1.3008 m2/g和1.6408m2/g,表明碳纳米管对信息激光具有显著的消光效果。     

Spectral measurement of acceptor-to-donor extinction coefficient ratio in living cells

This report presents a simple method named as sp-ECR to determine the molar extinction coefficient ratio (γ(λ_ex)) of acceptor-to-donor in living cells at excitation wavelength λ_ex, which is closely associated with the acceptor cross-excitation, the hardest issue of FRET quantification. sp-ECR determines γ(λ_ex) by spectrally unmixing the emission spectrum of a donor–acceptor tandem construct under λ_ex excitation without any additional references, such that this method can be performed under optimal imaging condition. We used sp-ECR to measure the γ(458) of Venus/Cerulean in living HepG2 cells on a confocal microscope, and the measured values were consistent with those obtained by lux-FRET method. We also used sp-ECR to measure the γ(458) values of Venus/Cerulean and YFP/CFP as well as YFP/GFP, the commonly used FRET FPs pairs in other two kinds of cancer cell lines on the confocal microscope, and found that the extinction coefficients of FPs depended on cell lines. After predetermining the γ(458) of Venus to ECFP, we used sp-ECR method to monitor the staurosporine (STS)-induced dynamical caspase-3 activation in single live A549 cells expressing SCAT3 by spectrally resolving the absolute FRET efficiency of SCAT3, and found that STS-induced caspase-3 activation in single cells is a very rapid process within 20 min.     

Maximum coefficient of light extinction in a nonabsorbing dispersive medium

The maximum value of the light extinction coefficient μ, which can be observed in a dispersive medium with a relative refractive index n of the scattering particles, is studied within the framework of a quasi-crystalline approximation for nonabsorbing dispersive media consisting of monodisperse spherical scatterers. A change in the diffraction parameter x of the scattering particles and their volume concentration c _v is accompanied by nonmonotonic variations of the extinction coefficient, and the function μ(x, c _v ) exhibits several maxima. The dimensions and concentrations of particles are determined, for which the extinction coefficient reaches the absolute maximum μ^max. The μ^max value exhibits a monotonic growth with increasing relative refractive index n of the scattering particles. The conditions of validity of the Ioffe-Regel criterion of radiation localization have been studied. It is established that the localization in nonabsorbing dispersive media can be observed only for n ? 2.7. The intervals of x and c _v in which the criterion of radiation localization is satisfied in dispersive media consisting of particles with n = 3.0 and 3.5 are determined.     

Interference method of measuring the extinction coefficient of birefringent optical fibers

The extinction coefficient of a birefringent optical fiber (the ratio between the radiation power output of the polarization mode and the radiation power transferred from this mode to another one) characterizes the capability of a birefringent fiber to retain the polarization state of the radiation. In relatively short birefringent fibers (1–100 m), the extinction coefficient may reach 10⁴–10⁶. Such high values of the extinction coefficient are difficult to measure by standard techniques (excitation of one polarization mode by an incoherent source with subsequent recording of the light intensity at the output of the analyzer). An interference method of measuring the extinction coefficient of birefringent fibers is suggested. It is based on using a coherent source and measuring interference oscillations caused by an additional phase modulation at the input of the fiber. This method does not require precise polarization matching between the laser source and fiber and considerably loosens requirements for the polarizer-analyzer extinction and resolution of the photodetector. As a result, using simple standard components (semiconductor laser, film polarizer, and photodetector), one can measure extinction coefficient as high as 10⁶. The suggested interference method of measuring the extinction coefficient of birefringent fibers receives a theoretical analysis, and experimental data obtained for 2- to 1000-m-long fibers are presented.     

弱吸收多层薄膜消光系数的反演

从窄带干涉滤光片的峰值透射率测量可以直接反演出弱吸收薄膜的消光系数，从而得到一种能简易而又精确地评价多层薄膜微弱吸收的新方法. 推导了弱吸收窄带干涉滤光片的吸收表达式， 阐述了确定弱吸收薄膜消光系数的基本原理.以离子束溅射的Ta₂O5/SiO₂波分复用滤光片为例，分析了这种评价方法的基本精度. 关键词： 光学测试 离子束溅射 光学薄膜干涉滤光片 消光系数     

Optical absorption coefficient of the first series transition metals between 20 and 130 eV

Experimental electron-energy loss spectra are used to calculate in a rather accurate way the complex dielectric constant and consequently the optical absorption coefficient.     

Reflection coefficient and depth extinction coefficient of a semiinfinite layer of a dispersed medium

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 1, pp. 137–142, January, 1990.     

An electroreflectance study of gallium antimonide in the 3.0–4.2 eV region

Results of an electroreflectance investigation of gallium antimonide in the 3.0–4.2 eV region are presented. The observed recurrence in this region of the spin-orbit splitting of the zone-center valence band states suggests a revised assignment for the observed recurrence in this region of the spin-orbit splitting of the zone-center valence band states suggests a revised assignment for the observed structure in terms of transitions to the second conduction band states.     

Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.     

共上能级三能级二聚物蒸气系统增益系数测量

本文提出了一种能够测量单纯由粒子数反转造成的增益系数的方法,给出了考虑几何因素及吸收影响之后修正了的实验计算公式,并对Na_2B~1Ⅱ_u—X~1∑_g~+跃迁增益系数进行了测量。     

Optical properties of InSe from 2 eV to 25 eV

The reflectivity spectrum of InSe between 2 and 25 eV is reported. From experimental results the optical functions are computed and a conduction band density of states is proposed. A comparison is made with a previous pseudopotential band structure calculation.     

从吸收比计算光学薄膜的消光系数

对于弱吸收薄腹,当薄膜和基底的折射率在一定数值范围内时,含有吸收比的公式可以用来计算薄膜的消光系数.该式不能用来计算已经没有干涉效应的厚的强吸收膜的消光系数.     

用消光系数比表征火灾烟雾的分类特征

提出了一种表征火灾烟雾分类特征的方法,采用两个已知波长的消光系数的比值表征火灾烟雾的本质特征.研究表明:两个已知波长的消光系数比仅与烟雾粒子群的粒径分布、平均粒径和折射率有关,排除了烟雾粒子浓度的影响,通过对火灾烟雾进行简单的光学测量和计算,即可得到火灾烟雾的分类特征 关键词： 消光系数比 火灾烟雾 分类特征     

Ultraviolet Raman lidar for high-accuracy profiling of aerosol extinction coefficient

An ultraviolet （UV） Raman lidar system at 354.7 nm has been developed for accurately measuring the aerosol extinction profiles. A spectroscopic filter combining a high-spectral-resolution grating with two narrowband mirrors is used to separate the vibrational Raman scattering signal of N2 at a central wavelength of 386.7 nm and the elastic scattering signal at 354.7 nm. The aerosol extinction is derived from the Raman scattering of N2 and the elastic scattering by the use of Raman method and Klett method, respectively. The derived results of aerosol extinction are used to compare the difference of two retrieval methods, and the preliminary experiment shows that the Raman lidar system operated in analog detection mode has the capability of measuring aerosol profiles up to a height of 3 km with a laser energy of 250 mJ and an integration time of 8 min.