文献类型：期刊文献

英文题名：Experimental Investigation of Mechanisms of Forming RbH by Irradiating a Rb+H₂ Mixture with Laser Light

作者：Shen Xiao-yan[1];Liu Jing[2];Dai Kang[2];Shen Yi-fan[2]

机构：[1]E China Univ Sci & Technol, Dept Chem, Shanghai 200237, Peoples R China;[2]Xinjiang Univ, Dept Phys, Urumqi 830046, Peoples R China

年份：2008

卷号：28

期号：11

起止页码：2487

外文期刊名：SPECTROSCOPY AND SPECTRAL ANALYSIS

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000261459900006)】；

语种：英文

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

摘要：The radiation of a laser photoexcited Rb atoms from the ground state to the 5P(3/2) level in a mixture of Rb vapor and hydrogen. The energy-pooling collision 5P(3/2)+5P(3/2)-> 5S(1/2)+5D producted 5D state. The Rb(5P(3/2)) density and spatial distribution were mapped by monitoring the absorption of a counter-propagating laser beam, tuned to the 5P(3/2)-> 7S(1/2) transition, which could be translated parallel to the pump bean-L In the presence of radiation trapping, the spontaneous radiation rate is multiplied by the transmission factor T-5P3/2 -> 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 T-5P3/2 -> 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 D line as a function of the H-2 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 (5P(3/2))+H-2 (upsilon=0)-> Rb(5S)+H-2 (upsilon=2) producted state H-2 (upsilon=2). This process is at least 16 times faster than the Rb (5P(3/2)) 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 H-2 (upsilon=2)+H-2 (upsilon= 0)-> H-2 (upsilon=1)+H-2 (upsilon= 0)+3 920.2 cm(-1) is 7.7 x 10(-19) cm(2). Hence the relaxation rate of this vibrational level is relatively slow and the nuclear spin statistics is conserved. The H-2 (upsilon=2) density was determined by using the cross section for Rb(5P(3/2))-H-2 quenching. RbH was fromed by the Rb(5D)+H-2 and Rb (5P(3/2))+H-2 (upsilon=2) reactions and observed by laser absorption. The ratio of 5D -> 5P(3/2) to 5P(3/2)-> 5S(1/2) fluorescence was measured as a function of the H-2 density. The absorption of the laser beam tuned to the X-1 Sigma(+)-> A(1)Sigma(+) line of RbH was also measured as a function of the H-2 density. From these measurements we obtained the cross section of 4.02 x 10(-17) cm(2) for the process Rb (5D)+H-2 -> RbH+H. The cross section for Rb(5P(3/2))+H-2 (upsilon=2)-> RbH+H is 1.00 x 10(-18) cm(2). This experiment showed that under our experimental conditions, RbH molecules are not created by a direct interaction of Rb(5P) with H-2 but through a two-step reaction.