文献类型：期刊文献

中文题名：激光激发Rb+H_2系统形成RbH分子机理的实验研究

英文题名：Experimental Investigation of Mechanisms of Forming RbH by Irradiating a Rb+H_2 Mixture with Laser Light

作者：沈晓燕[1];刘静[2];戴康[2];沈异凡[2]

机构：[1]华东理工大学化学与分子工程学院,上海200237;[2]新疆大学物理科学与技术学院,新疆乌鲁木齐830046

年份：2008

卷号：28

期号：11

起止页码：2487

中文期刊名：光谱学与光谱分析

外文期刊名：Spectroscopy and Spectral Analysis

收录：CSTPCD;;EI(收录号：20085011777529);Scopus;北大核心:【北大核心2004】；CSCD:【CSCD2011_2012】；PubMed;

基金：国家自然科学基金项目(10664003)资助

语种：中文

中文关键词：激光化学;碰撞能量转移;荧光;光吸收;RbH分子

外文关键词：Laser chemistry,Collisional energy transfer,Fluorescence,Optical absorption,RbH

摘要：在Rb-H2混合系统中用激光(泵浦激光)将基态Rb原子激发到Rb(5P3/2)能级,将调谐至5P3/2→7S1/2跃迁的另一激光束(检测激光)与泵浦激光反向平行通过样品池,并在池的直径方向平行移动,利用光学吸收法得到Rb(5P3/2)态的密度及其空间分布。由于辐射陷获存在,有效辐射率是自然辐射率与透射因子(发射的光子在探测区域内没有被吸收的平均概率,它与吸收截面及激发态原子密度和空间分布有关)的乘积。由5P3/2原子密度及其空间分布结合5P3/2←5S1/2跃迁线的碰撞增宽计算了透射因子。能量合并过程5P3/2+5P3/2→5S1/2+5D产生高位态5D原子,猝灭过程Rb(5P3/2)+H2(v=0)→Rb(5S)+H2(v=2)产生H2(v=2)态,H2(v=2)密度由Rb(5P3/2)与H2的碰撞猝灭截面得到。Rb(5D)+H2和Rb(5P3/2)+H2(v=2)发生碰撞反应可生成RbH分子,通过对不同H2密度时5D→5P3/2与5P3/2→5S1/2荧光强度比以及RbH分子X1Σ+→A1Σ+跃迁线吸收光强的测量,首次得到了Rb(5D)+H2→RbH+H和Rb(5P3/2)+H2(v=2)→RbH+H的反应截面分别为4.02×10-17cm2和1.00×10-18cm2。实验表明,Rb(5P3/2)+H2不直接生成RbH分子,而是通过二步反应产生的。
The radiation of a laser photoexcited Rb atoms from the ground state to the 5P3/2 level in a mixture of Rb vapor and hydrogen.The energy-pooling collision 5P3/2＋5P3/2→5S1/2＋5D producted 5D state. The Rb（5P3/2）density and spatial distribution were mapped by monitoring the absorption of a counter-propagating laser beam,tuned to the 5P3/2→7S1/2 transition,which could be translated parallel to the pump beam.In the presence of radiation trapping,the spontaneous radiation rate is multiplied by the transmission factor T5P3/2→5S1/2,which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed.The T5P3/2→5S1/2 is related to the frequency dependent absorption cross section and the density and spatial distribution of atoms in the level of the transition.The effective radiative rates of the Rb D2 line as a function of the H2 pressure were obtained.These quantities were combined with the measured excited atom density and fluorescence ratio to yield absolute energy-pooling rate coefficient.The quenching collision Rb（5P3/2）＋H2（v=0）→Rb（5S）＋H2（v=2） producted state H2（v=2）.This process is at least 16 times faster than the Rb（5P3/2） radiative decay rate. The reverse process of this process is relatively unlikely due to their large translational energy defect.The cross section for the process H2（v=2）＋H2（v=0）→H2（v=1）＋H2（v=0）＋3 920.2 cm-1 is 7.7×10-19 cm2.Hence the relaxation rate of this vibrational level is relatively slow and the nuclear spin statistics is conserved.The H2（v=2） density was determined by using the cross section for Rb（5P3/2）-H2 quenching.RbH was fromed by the Rb（5D）＋H2 and Rb（5P3/2）＋H2（v=2） reactions and observed by laser absorption.The ratio of 5D→5P3/2 to 5P3/2→5S1/2 fluorescence was measured as a function of the H2 density.The absorption of the laser beam tuned to the X1Σ＋→A1Σ＋ line of RbH was also measured as a function of the H2 density.From these measurements we obtained the cross section of 4.02×10-17 cm2 for the process Rb（5D）＋H2→RbH＋H.The cross section for Rb（5P3/2）＋H2（v=2） →RbH＋H is 1.00×10-18 cm2.This experiment showed that under our experimental conditions,RbH molecules are not created by a direct interaction of Rb（5P） with H2 but through a two-step reaction.