Photoassociative laser-induced fluorescence of XeCl* and kinetics of XeCl(<i>B</i>) and XeCl(<i>C</i>) in Xe

Abstract

Laser induced fluorescence studies have been done with XeCl molecules, which demonstrate photoassociation (free–bound absorption) as well as conventional bound–bound absorption from the XeCl(X) van der Waals molecules. The XeCl(X) and Xe+Cl pairs were generated by a pulsed dc discharge through 1–6 Torr Xe/Cl2 mixtures. Experiments also were done with Xe/HCl mixtures. The time and wavelength resolved XeCl(B–X) and XeCl(C–A) excitation and fluorescence spectra are reported. Model calculations were done to demonstrate that the laser excitation spectra for XeCl(B,v=0−3) show laser-assisted photoassociation. The time resolved decay of the XeCl(B,v′=0) and XeCl(C,v′=0,1) states was used to measure the radiative lifetimes 11.1±0.2 and 131±10 ns, respectively, and the XeCl(B) and XeCl(C) coupling and quenching rate constants. The transfer and quenching rate constants for XeCl(B) by Xe are assigned as (11±1)×10−11 and (2.3±0.3)×10−11 cm3 molecule−1 s−1, respectively; although, the sum is known with greater certainty than the individual values. The quenching rate constants of XeCl(B,v′=0) by Cl2 and HCl are (4.3±0.2)×10−10 and (6.3±0.5)×10−10 cm3 molecule−1 s−1. Evidence is presented to show that the B–C coupling rate constants are comparable to the XeCl(B,C) vibrational relaxation rate constants for XeCl(B,v′=2) in collisions with Xe.