Selective dissociation of HCl in Kr from vibrational overtones

Abstract

Vibrational levels v=1, 2, and 3 of HCl in Kr matrices are populated with tunable IR radiation and the excited molecules are dissociated by UV excitation to the repulsive A 1∏ state. Cl fragments are recorded by laser induced fluorescence of Kr2Cl and dissociation rates are determined from the increase in LIF with UV dose. The enlarged UV Franck–Condon range for overtones allows the study of cage exit of H fragments with small kinetic energy Ekin. A threshold at Ekin=1.4 eV and a steep rise indicate a predominant sudden exit. Monomers, different initial rotational states and transients in the relaxation cascade are preselected with overtone excitation and the feasibility of a discrimination between isotopes, aggregates, and local structures is illustrated.