Excitation of hydrogen atom by ultrashort laser pulses in optically dense plasma

The features of excitation of a hydrogen atom by ultrashort laser pulses (USP ) with a Gaussian envelope in optically dense plasma at a Lyman‐beta transition are studied theoretically. The problem is of interest for diagnostics of optically dense media. USP have two doubtless advantages over conventional laser excitation: (a) the USP carrier frequency is shifted to the region of short wavelengths allowing exciting atoms from the ground state and (b) the wide spectrum of USP allows them to penetrate into optically dense media to much longer distances as compared with monochromatic radiation. As actual realistic cases, two examples are considered: hot rarefied plasma (the coronal limit) and dense cold plasma (the Boltzmann equilibrium). Universal expressions for the total probability of excitation of the transition under consideration are obtained in view of absorption of radiation in a medium. As initial data for the spectral form of a line, the results of calculations by methods of molecular dynamics are used. The probability of excitation of an atom is analysed for different values of problem parameters: the pulse duration, the optical thickness of a medium, and the detuning of the pulse carrier frequency from the eigenfrequency of an electron transition.     

基于高斯光束特性的Mie散射大气激光雷达回波近场信号校正研究

介绍一种基于高斯光束传输特性对Mie散射激光雷达回波信号校正的新方法.首先根据发射激光束的高斯光束特性，对大气激光雷达回波信号作高斯修正，然后在大气近似均匀假定下，对近场区经高斯修正的回波信号距离校正函数进行二次曲线拟合，实现对交叠面积影响的修正，实际计算表明，用此方法对Mie散射激光雷达回波近场信号进行处理，可获得与实际更为接近的反演结果. 关键词： 大气激光雷达 高斯光束 回波近场信号修正 大气消光系数     

稠密共振介质中近偶极-偶极相互作用的局域场效应

 为研究存在由近偶极-偶极相互作用诱导的局域场效应时超短强激光脉冲与稠密共振介质相互作用的特性,采用光与物质相互作用的半经典理论,建立了稠密二能级体系中考虑原子间近偶极-偶极相互作用的修正光学Bloch方程,并用四阶Runge-Kutta法数值求解了该方程。研究结果表明:局域场效应对稠密二能级体系中Bloch矢量的瞬态相干过程和稳态性质都具有强烈的调制作用。并由此提出了调控稳态粒子数布居的两种方案。     

Molar extinction coefficients of IR absorption bands of Cu(II) dipivaloylmethanate

IR absorption spectra of an intracomplex chelate compound of Cu(II) bis-dipivaloylmethanate in the spectral range 4000–300 cm⁻¹ are investigated. A comparison is made between the spectra of the complex in different aggregative states: as a solution in heptane and as condensed films. The molar extinction coefficients of absorption bands are calculated. The extinction coefficients found are used to evaluate the thickness of Cu(dpm)₂ films. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 34–37, January–February, 2000.     

稠密共振介质中近偶极-偶极相互作用的局域场效应

为研究存在由近偶极-偶极相互作用诱导的局域场效应时超短强激光脉冲与稠密共振介质相互作用的特性,采用光与物质相互作用的半经典理论,建立了稠密二能级体系中考虑原子间近偶极-偶极相互作用的修正光学Bloch方程,并用四阶Runge-Kutta法数值求解了该方程。研究结果表明:局域场效应对稠密二能级体系中Bloch矢量的瞬态相干过程和稳态性质都具有强烈的调制作用。并由此提出了调控稳态粒子数布居的两种方案。     

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。     

Molar extinction coefficients of some carbohydrates in aqueous solutions

Molar extinction coefficients of some carbohydrates viz. l-arabinose (C₅H₁₀O₅), d-glucose (C₆H₁₂O₆), d-mannose (C₆H₁₂O₆), d-galactose (C₆H₁₂O₆), d(-) fructose (C₆H₁₂O₆) and maltose (C₁₂H₂₄O₁₂) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well.     

Measurement of optical constants for dense media by low-coherence dynamic light scattering

We perform the optical constants measurements for different absorption dense media by low-coherence dynamic light scattering (DLS) technique. The estimated particle size is used to calculate the scattering coefficient of particles suspended in dense media. The path-length resolved intensity distributions of light backscattered from the absorbing dense media are investigated experimentally by virtue of path-length resolved performance in low-coherence DLS measurements. The absorption coefficient can be obtained by applying the measured path-length resolved intensity distributions to the modified Lambert-Beer law. As a result, we proposed a new low-coherence DLS technique in simultaneous measurement of the scattering and absorption coefficients of absorbing dense media.     

Molar coefficients of extinction for IR absorption bands of Ni(II) acetylacetonate, ketoiminate, and trifluoroacetylacetonate

We have studied IR absorption spectra (within the spectral range of 4000-200 cm⁻¹ of the intracomplex chelate compounds Ni(II) bis-acetylacetonate, Ni(II) bis-ketoiminate, and Ni(II) bis-trifluoroacetylacetonate and have given a full interpretation and comparison of the spectra of these compounds in dissolved and solid states. The reasons for the differences in the spectra are discussed. The molar coefficients of extinction for the absorption bands are calculated. Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3, Akad. Lavrent’ev Ave., Novosibirsk, 630090, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 775–780, September–October, 1998.     

Characterization and imaging in optically scattering media by use of laser speckle and a variable-coherence source

We demonstrate the application of laser-speckle statistics formed by a variable-coherence source illuminating a scattering medium, for determining the scattering parameter mu;(s)>(?) of a diffusion model for the medium. Furthermore, we apply this technique to visualize laterally localized inhomogeneities embedded within a highly scattering sample.     

Measurement of tropospheric CO2 and aerosol extinction profiles with Raman lidar

A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigatious.The third harmonic of Nd:YAG laser (354.7-nm wavelength) was used as stimulated light source to provide nighttime measurements.Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively.To improve the real time monitoring function,a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient.Typical features of CO2 concentration profile and aerosol extinction coefficient in Herei were presented.The mixing ratio of atmospheric CO2 in Hefei can reach about 360-400 ppmv.     

飞秒啁啾Gauss型脉冲在稠密Λ型三能级原子介质中的传播

利用由预估校正(PC)- 时域有限差分(FDTD)法求得的不含慢变包络近似(SVEA)和旋转波近似(RWA)的全波Maxwell-Bloch方程的数值解, 研究了飞秒啁啾Gauss型激光脉冲(以下简称啁啾脉冲)在稠密Λ型三能级原子介质中的传播.研究表明,啁啾系数(C)的正负及大小的变化对脉冲传播特性有显著的影响,而且这个影响与脉冲面积的大小密切相关.面积小于4π的啁啾脉冲,在介质中传播时不发生分裂,且啁啾脉冲逐渐演化为一个近似的无啁啾(C=0)脉冲,这一特点不随啁啾系数的改变而     

Ratio of aerosol backscatter to extinction coefficients as determined from angular scattering measurements for use in atmospheric lidar applications

Wavelength dependence as well as relative humidity dependence of aerosol extinction to backscatter ratio was examined. The extinction to backscatter ratio is essential in solving lidar signal and was estimated from aerosol size distribution and refractive index (which were derived from angular light scattering measurements) using the Mie scattering theory. The extinction to backscatter ratios were calculated for wavelengths of 355 nm, 532 nm, 694 nm and 1064 nm, the major laser wavelengths used for lidars, where the refractive indices were assumed to be constant with wavelength. p ]When relating the aerosol extinction ₁ to the backscatter ₁ with a functional form of _{1 1} k ₁, the exponentk ₁ was evaluated by the least square method and tabulated for the four wavelengths. The extinction to backscatter ratio defined asS ₁= ₁/ ₁ was calculated and their dependence on the wavelength and relative humidity was examined. Their dependence on the relative humidity is small whileS ₁ in the average takes the value of 66 (±17), 60 (±13), 52 (±13) and 42 (±11) for the wavelengths 355 nm, 532 nm, 694 nm and 1064 nm, respectively     

气溶胶前向散射大气能见度测量系统传递系数的标定及校准方法

分析了气溶胶的前向角散射特性,利用标准的大气透射仪标定前向散射大气能见度测量系统的传递系数。当系统结构发生变化时,传递系数也随之改变,为保证系统测量的准确性和简化系统传递系数的标定过程,提出了一种利用标准漫透射板校准系统传递系数的方法。该方法使用了两块具有相同透射系数的漫透射板,使气溶胶粒子团在前向半球上产生漫散射,此时探测器的测量值即为包含了仪器常数的定值。当系统结构改变时,这个测量值相对于原测量值的变化率作为比例系数代入系统传递系数的计算,实现校准。     

温稠密物质中不同价态离子分布对X-射线弹性散射光谱计算的影响

在天体物理和惯性约束聚变研究中涉及到的温稠密物质通常包含多种元素的混合,并且每种元素还被电离成多种离子价态,不同价态离子结构及其丰度将直接影响温稠密物质的诊断及其物理性质.同时,从电子结构计算出发来研究宏观物理性质时,还需要考虑温度、密度效应对离子结构的影响.本文从不同价态离子的电子结构计算出发,采用考虑了离子间相互作...     

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用高密度等离子体模型可以计算出一整套输运参数,并且在很宽的等离子体温度和密度范围内有合理的精度,可广泛应用于Z箍缩等离子体、激光聚变和磁约束聚变等领域,并将这个模型计算出的各种输运参数拟合成了实用的公式。     

Monte-Carlo simulation of light scattering in fractal porous media

Monte-Carlo simulation of light propagation in a porous medium with a mass fractal morphology was carried out. It was shown that the simulation results can be used to analyze experimental data on light scattering and to study the porous medium structure. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 193–196, March–April, 2008.     

东南沿海地区相对湿度对气溶胶消光特性的影响

采用能见度仪和温度脉动仪在我国东南沿海典型地区进行能见度和相对湿度测量实验,利用能见度与消光系数和波长的关系,分析了在雾霾和晴好两种天气条件下相对湿度对沿海气溶胶系统消光系数的影响。研究结果表明:对于波长为1.06 m的激光,该地区两种天气下气溶胶粒子的潮解点均为80%左右;当相对湿度在80%~90%时,随着相对湿度增大,两种天气下消光系数相对干粒子时的增长率基本相同,吸湿增长因子主要介于1~2;当相对湿度大于90%时,二者相对增长差别很大,晴好天气下吸湿增长因子增大了两个量级,远大于雾霾天气。     

激光产生温稠密物质的微观动力学过程及状态诊断

随着大型激光装置的建立和精密测量技术的发展,强激光与固体相互作用成为实验室产生温稠密物质的一个重要手段。温稠密物质的结构复杂性、瞬态性和非平衡性给理论建模和实验测量带来了巨大挑战。本文系统介绍了激光产生温稠密物质的实验手段和理论模拟方法方面的重要进展,分析了其中的电子激发动力学、电子-离子能量弛豫过程、离子动力学等物理过程,总结了温稠密物质状态诊断的实验技术和理论方法,并论述了激光产生温稠密物质的发展趋势。