Nonequilibrium vibrational populations and dissociation rates of HCl under IR laser pumping

Nonequilibrium vibrational distributions and dissociation rates of HCl under IR laser pumping of suitable frequency have been calculated by solving a system of vibrational master equations including optical pumping, V-V (vibration-vibration) and V-T (vibration-transition) energy exchanges. The results show that under a laser pump of 106s-1 dissociation of HCl can occur as a result of the V-V up-pumping mechanism, which transports up to the top of the HCl vibrational ladder the vibrational quanta introduced by the laser pump over the first few vibrational levels of HCl. The influence of the gas temperature T on the dissociation rate is discussed either for the isothermal problem or for the nonisothermal one. At high pumping rates an increase of T decreases the dissociation rate (300 K < T < 1000 K) as a result of the destruction of V-V up-pumping mechanism at high temperature. (author)