Relaxation of HCl(v= 1) and DCl (v= 1) by chlorine atoms at temperatures between 195 and 400 K

Abstract

A pulsed HCl chemical laser has been used to excite HCl in the presence of known concentrations of Cl atoms in a discharge-flow apparatus. By observing the subsequent vibrational fluorescence as a functions of time, rates of relaxation of HCl(v= 1) by Cl atoms were determined at temperatures between 195 and 400 K. The values of the rate constant, k1,H, can be matched quite well by the Arrhenius expression: k1,H= 9.0 (+1.8–1.6)× 10–11 exp(–5.8 ± 0.5 kJ mol–1/RT)cm3 molecule–1s–1. Similar experiments on DCl yielded k1,D= 2.4(+0.6–0.5)× 10–11 exp(–3.2 ± 0.9 kJ mol–1/RT) cm3 molecule–1 s–1. Possible mechanisms for these unusually rapid relaxation processes are considered.