He与HD、HT、DT碰撞的转动激发研究

采用Tang-Toennies势模型,通过坐标变换,得到了氦原子与氢的非对称同位素替代分子体系在质心坐标系中的势能函数.在此基础上,计算了上述体系的低能碰撞转动激发截面.文中最后讨论了氦原子与氢的非对称同位素替代体系碰撞的微分截面的变化规律     

He同位素对He-NO碰撞体系微分截面的影响

用密耦近似方法计算了同位素He原子与NO分子碰撞体系的总微分截面、弹性微分截面和非弹性微分截面,总结了同位素He原子对He-NO碰撞体系微分截面的影响. 计算结果表明：在同一入射能量下,随着入射同位素He原子质量增加,总微分截面在0°时的角分布逐渐增大;同位素He原子与NO分子碰撞发生的彩虹现象越明显. 同时,体系约化质量增加的效应大于相对碰撞速度减小的效应,使散射振荡间隔逐渐减小. 关键词： He-NO 密耦近似 微分截面 同位素效应     

3He4He与H2分子碰撞的同位素效应研究

用公认精确度较高的密耦近似方法计算了入射能量E=0.5eV时惰性气体原子3He(4He)与H2分子替代碰撞体系的转动激发碰撞截面.通过分析3He(4He)-H2碰撞体系分波截面和微分截面的差异,总结出在氦原子的同位素替代情形下3He(4He)-H2碰撞体系分波截面和微分截面随分波数增加和同位素原子质量改变的变化规律.     

不同能量的氦原子与同位素分子H2(D2,T2)碰撞分波截面的理论计算

用Tang-Toennies势模型和密耦近似方法计算了不同能量下惰性气体原子He与H2及其同位素D2,T2替代碰撞体系的振转激发碰撞截面.通过分析He-H2(D2,T2)各碰撞体系分波截面的差异,总结出在H2分子的对称同位素替代情形下He-H2(D2,T2)碰撞体系分波截面随量子数和体系约化质量变化的规律.结果表明,体系的约化质量及入射原子相对碰撞能量的变化均给体系的碰撞截面带来不同程度的影响.     

非对称同位素替代分子HD、HT和DT分子与氦原子(E=0.1 eV) 碰撞角分布计算

当入射氦原子能量E=0.1 eV时,用密耦方程(Close Coupling Equation)计算非对称同位素替代分子HD、DH-He碰撞的弹性和非弹性散射的角分布.     

Ne同位素替代下Ne-HF碰撞截面的理论计算

采用Huxley势函数拟合QCISD(T)/ aug-cc-pVTZ计算的相互作用势能面,通过精确度较高的密耦近似方法计算了E=100 meV时,氖原子的三种同位素 ¹⁶Ne, ²⁰Ne, ³⁴Ne与HF分子碰撞系统的微分截面和分波截面.探讨了Ne的同位素替代引起的Ne-HF碰撞激发 截面的变化规律.     

氢(氘、氚)的非对称同位素替代分子与低能氦原子(E=0 .1 eV) 碰撞分波截面研究和计算

当入射氦原子能量E=0.1 eV时,用密耦方程(Close Coupling Equat ion)研究和计算了氢的非对称同位素替代分子HD、TD、DT-He碰撞.首先考虑了非对称同位素替代时质心偏移量对势能函数的影响,得到在新质心坐标系中势能函数表达式,并计算了 E=0.1 eV时弹性碰撞00-00分波及非弹性碰撞激发00-01、00-02、00-03、00-04分波截面.     

3He(4He)与H2分子碰撞的同位素效应研究

用公认精确度较高的密耦近似方法计算了入射能量E=05eV时惰性气体原子³He(⁴He)与H₂分子替代碰撞体系的转动激发碰撞截面.通过分析³He(⁴He)-H₂碰撞体系分波截面和微分截面的差异,总结出在氦原子的同位素替代情形下³He(⁴He)-H₂碰撞体系分波截面和微分截面随分波数增加和同位素原子质量改变的变化规律. 关键词： 散射截面 密耦方法 同位素替代 散射角     

氦同位素原子与钠分子碰撞转动激发积分散射截面的理论计算

多体刚性椭球模型是一种比较精确的描述氦原子与钠分子碰撞的理论模型.本文用多体刚性椭球模型计算了不同能量下He的同位素原子3He,4He,7He,10He与Na2分子碰撞的转动激发积分散射截面,表明增加椭球等势面个数可以得到更准确的转动激发积分散射截面;总结出3He,4He,7He,10He-Na2碰撞体系转动激发积分散射截面随相对入射能量和体系约化质量变化的规律;讨论了相对入射能量为100meV时,相互作用势的不同区域对4He-Na2碰撞体系转动激发积分散射截面的影响情况.     

不同能量下He原子与HCl分子碰撞激发分波截面的同位素效应研究

基于Huxley势函数的拟合势,通过精确度较高的密耦近似方法计算了入射能量为50meV和150meV时,氦原子的四种同位素3He,4He,9He,10He与HCl分子碰撞体系的激发分波截面.通过分析不同能量下,各碰撞体系分波截面的差异,探讨了不同入射能量时He的同位素对He-HCl碰撞体系的分波截面的影响,总结出其分波截面随量子数和体系约化质量的变化规律.     

Cross sections for rotational excitation in He－H2 collisions

Close coupling calculations have been carried out for rotational excitations in He－H₂ collisions with symmetric isotopic substitution (He－H₂, D₂, T₂) and asymmetric isotopic substitution (He－HD, HT, DT). Cross sections have been obtained at the incidence energy of 0.3eV. Based on the calculations, the effect of isotopic substitution on atom－diatom collisions is discussed.     

Vibrational Spectra of Cd(NH3)2Br2 with 2H Isotopic Substitution and Local Symmetry Force Field

The infrared and Raman spectra of the cadmiumdiammindibromide with ²H - isotopic substitution, have been measured. In order to examine the transferabilities of the skeletal and -NH₃, ligand force constants, a normal coordinate analysis was carried out based on a Local Symmetry Force Field (LSFF). The results support the experimental assignments.     

Microwave spectra and centrifugal distortion constants of formic acid containing 13C and 18O: Refinement of the harmonic force field and the molecular structure

Pure rotational spectra of H¹³COOH, HC¹⁸OOH, and HCO¹⁸OH have been measured in the frequency region 8–185 GHz. Analysis of the spectra has given improved rotational constants and quartic and sextic centrifugal distortion constants. The quartic distortion constants have been combined with previously published distortion constants of four other isotopic species, and with the vibrational wavenumbers of seven isotopic species, to produce a refined harmonic force field. An improved substitution structure and the ground state average structure have been obtained. Some unmeasured transition frequencies which may be of importance in radioastronomy are also presented.     

不同能量下He原子与HCl分子碰撞激发分波截面的同位素效应研究

基于Hux1ey势函数的拟合势,通过精确度较高的密耦近似方法计算了入射能量为50 meV和150meV时,氦原子的四种同位素3He,4He,9He,10He与HCl分子碰撞体系的激发分波截面.通过分析不同能量下,各碰撞体系分波截面的差异,探讨了不同入射能量时He的同位素对He-HCl碰撞体系的分波截面的影响,总结出其分波截面随量子数和体系约化质量的变化规律.     

The effect of uncertainty in the eigendata of the pure host lattice on Greens-function calculations

The effect of the uncertainty in the eigendata of KI on gapmode calculations using the Greens-function technique has been examined. Certain eigenfrequencies calculated with the Shell-model could be compared with experimental singularities in the induced acoustic spectrum of KI containing impurities. Changing the theoretical eigenfrequencies to the experimental values for insertion in the isotopic substitution model, which was used as a testcase for Greens-function calculations, resulted in an appreciable shift (?0.3 cm^?1) in a gapmode frequency.     

Coherent neutron scattering by light water (H2O) and a light-heavy water mixture (64 per cent H2O/36 per cent D2O)

Measurements have been made, with high statistical accuracy, of the differential scattering cross-section for 1·06 Å neutrons by light water and a special mixture of light and heavy water at 22°C. For light water, the structure in the scattering pattern is attributed mainly to coherent scattering; a structure factor has been obtained over a limited range of momentum transfer. For the chosen mixture, the protons and deuterons give no contribution to the coherent scattering and a structure factor has been obtained which corresponds very well to the oxygen-nucleus structure factor obtained from X-ray data. The results show the desirability of extending these high accuracy measurements using isotopic substitution methods as a means of obtaining the three partial structure factors for water. The method of isotopic mixtures is applicable to a wide range of proton containing liquids.     

Vibration-rotation theory and isotopic substitution in nonlinear triatomic molecules

In the interpretation of high-resolution data it is helpful to be able to relate the experimentally determined molecular constants, such as rotational constants, centrifugal distortion constants, and vibration-rotation interaction constants of a given molecule to those of its isotopically substituted variants. Results concerning the symmetric nonlinear triatomic molecule (XYX) have been given through the second order of approximation by previous workers. In this paper, extensions of the work to the fourth order of approximation and to the nonsymmetric nonlinear triatomic molecule (XYZ) are considered. These extensions are found to increase the algebraic complexity of the problem considerably, and results can generally be given in implicit form only. The approach used is one that emphasizes the isotopic invariants of the problem, i.e., those expressions which remain unchanged when applied to the various isotopic modifications of a given molecule under the assumption that the molecular force field and the molecular geometry remain unchanged under isotopic substitution.     

Experimental Structures of the Carbon Chains HC(7)N, HC(9)N, and HC(11)N by Isotopic Substitution

The effective structures (r(0)) of the three linear cyanopolyynes HC(7)N, HC(9)N, and HC(11)N have been determined to high accuracy by isotopic substitution, following detection in a supersonic molecular beam with a Fourier transform microwave spectrometer of all of the singly substituted rare isotopic species. For each chain, the lengths of the individual bonds have been determined to an accuracy of 0.001 ? or 0.1% toward the end of the chain and to 0.01 ? or 1.0% toward the center. The experimental structures are in excellent agreement with recent high-level theoretical calculations, or, in the case of HC(11)N, with extrapolation from HC(9)N. The three polyynes studied here represent the largest reactive carbon chain molecules for which accurate structures have been derived empirically. For HC(7)N and HC(9)N, it has been possible to resolve at high-resolution nitrogen hyperfine structure in the lower rotational transitions and determine eQq for all of the singly substituted isotopic species of HC(7)N and for normal HC(9)N. Copyright 2000 Academic Press.