Precise measurement of the depolarization ratio from photoacoustic Raman spectroscopy

A new method for the accurate determination of the Raman depolarization ratio is reported with an improved setup for photoacoustic Raman spectroscopy (PARS). The precise measurement is achieved by measuring the dependence of the acoustic signal intensity on the cross‐angle between the polarizations of two incident laser beams. We demonstrate this sensitive and simple method with several gaseous molecules, such as CH₄ and H₂. The measured results of depolarization ratios agree well with the theoretical values with an upper error limit of ± 0.005, which is comparable to that with polarization‐resolved CARS spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.     

反向泵浦的受激喇曼光声光谱

报道一种改进的受激喇曼光声光谱实验方法 (PhotoacousticRamanSpectroscopy ,PARS) ,该方法的主要特点是将两束激光以反向传播的方式重合 ,从而不仅克服了通常的实验方法 (两束激光通过双色镜片重合 )在测量小喇曼位移方面的限制 ,也使实验的操作更加简单 .在实验中 ,以CH4 分子为研究对象 ,一束波长为 5 3 2 .1nm的激光作为泵浦光 ,另一束可调谐激光作为探测光 (Stokes光 ) ,两束光相向作用于光声池内 ,在 62 5～ 64 2nm和 5 73～ 5 89nm得到了CH4 分子ν1 、ν2 和ν3模的PARS光谱 ,其结果与前人利用自发喇曼散射技术 (ORS)一致 ,其中喇曼活性较弱且喇曼位移较小的ν2 模的PARS光谱是新得到的     

CF自由基双光子共振增强多光子电离研究：3pRy dberg态的转动分析

利用Ar/CF4、Ar/CF2Cl2或Ar/CF3COOH混合气体的直流脉冲放电产生CF自由基,观测了260～360nm范围内转动分辨的CF自由基双光子共振增强多光子电离谱。分析表明,该段光 谱对应于CF自由基3pπD2Πr(ν'=2～6,r=3/2,1/2)←←X2Πr(ν"=0,r=3/2,1/2)的共振激发。对观测的振动带进行了转动分析,并获得了3p里德堡态的转动常数和自旋-轨道分裂值。     

R~(n+1)中的线性Weingarten超曲面的刚性定理

利用熟知的Cheng-Yau算子研究了欧氏空间R~(n+1)中的线性Weingarten超曲面,主要结果是有关标准球面的两个刚性定理.     

RRKM理论研究N(4S)+CH2X(X=F,Cl)的反应通道

采用RRKM理论和疏松过渡态模型计算了N(4S) +CH2 X(X =F ,Cl)反应的微正则速率常数和通道分支比 .计算结果表明 ,在较低的内能下 (E =2 80 .2 9kJ/mol) ,N(4S) +CH2 F的主要产物为NCHF +H ,占总产物的5 9.2 % ,次要产物为H2 CN +F ,占 37.4 % .而N(4S) +CH2 Cl反应在E =2 6 7.78kJ/mol时 ,主要产物是H2 CN +Cl,占 90 .3% ,NCHCl+H只占 9.0 % .在内能较高的时候 (取E =5 0 0 .0 0kJ/mol) ,N(4S) +CH2 F的主要通道并未变化 ,而N(4S) +CH2 Cl的主要通道变为NCHCl+H ,比例为 5 1.5 % ,H2 CN +Cl的比例降到 4 0 .4 % .     

完备α度量的相对抛物型仿射球(英文)

摘要:设y:M→Rⁿ⁺¹是一个光滑连通流形到实仿射空间Rⁿ⁺¹的局部强凸浸入超曲面,而且是一个定义在区域Ω（?）Rⁿ上的严格凸函数x_n+1=f（x₁,x₂,…,x_n）的图.在α相对法化下,相对抛物型仿射球满足一个四阶非线性偏微分方程组.本文证明了这类抛物型仿射球的一个新的Bernstein性质.     

Deuterium separation by multiphoton dissociation of dichlorofluoromethane

Absorption and dissociation probabilities of CHCl₂F and CDCl₂F were investigated by a pulsed CO₂ laser in the wavenumber region of largest selectivity for deuterium. The absorption of CHCl₂F, which is a difference band, can largely be suppressed by cooling. At 200 K and at 920 cm^–1 absorption selectivities up to 4000 were found by extrapolation. In the presence of buffer gas, CDCl₂F can be multiphoton excited nearly like a linear absorber (harmonic oscillator). This is interpreted by a nearly resonant collisional relaxation v₇ to v₂ and by the smallness of the cross anharmonicity x₂₇. The dissociation selectivityS was 24,000 at natural abundance. Such large values were measured by a chromatographic method.S depends only onp _D, the partial pressure of the deuterated species. This dependence is approximately ln Sp _D ^–1 . It can be rationalized by considering only the average energy transferred to the nonresonant molecules by collisions with CDCl₂F. The above functional shape is related to an Arrhenius type law. Comparison with trifluoromethane for D separation shows that CHCl₂F has primarily two advantages: its rapid H-D exchange with water and the less stringent requirements of laser energy and pulse length.A preliminary account of this work has appeared in Quantum Electr.2, 13 (1985) (in Chinese)     

Temperature effect on quenching of CH(AΔ)

The quenching rate constants of CH(A²Δ) radicals by alcohol, alkane, O₂, and C₂H₄ molecules over the temperature range 297–653 K have been measured using laser photolysis of CHBr₃ at 266 nm to produce CH(A) radical and time-resolved fluorescence measurements. Under the simultaneous effects of multiple attractive potentials and repulsive barrier, the temperature dependence of the quenching process of CH(A²Δ) is discussed qualitatively based on a modified collision complex model.     

Detailed balance in hyperfine structure with radiation trapping

In this paper, the validity of detailed balance in hyperfine structure was investigated in the presence of radiation trapping. It is shown that the detailed balance assumption will be valid so long as either the collisional transfer rate is large or the opacities are high enough, namely . Where R is the collisional transfer rate. A is the Einstein spontaneous emission coefficient. λ_i is the largest eigenvalue of radiation trapping integral operator of state i.