Energy disposal in the two-photon laser-assisted reaction in xenon and chlorine gas mixtures

The two-photon laser assisted reaction (LAR) in low pressure xenon and chlo rine gas mixtures has been studied over a broad range of excitation wavelen gths in order to characterize the role of the entrance channel in determini ng the vibrational state distribution of the reaction products. We measure a high degree of vibrational excitation in the XeCl* product, confirming ob servations from previous studies of the LAR of Xe+Cl-2 collision pairs [Ku , J. Phys. Chem. 87, 2989 (1983)], and in distinct contrast with the vibrat ionally cold excimer observed following laser excitation in molecular beam experiments [Boivineau , Chem. Phys. Lett. 128, 528 (1986)]. The mean vibra tional energy in the XeCl excimer depends strongly on laser wavelength, inc reasing with decreasing wavelength. Moreover, an increasing fraction of the available energy from the reaction is observed as vibration in the XeCl* p roduct as the laser is tuned toward shorter wavelengths. The reaction outco mes are interpreted in terms of a selectivity of initial conditions on the ionic potential surface that mediates the reactive collision. (C) 2000 Amer ican Institute of Physics. [S0021-9606(00)71447-4].