Electronic relaxation of Xe2Cl in gaseous and supercritical fluid xenon

Spectroscopic and kinetic studies of the triatomic Xe₂Cl exciplex in gaseous and supercritical fluid xenon up to 150 atm are reported. Clustering of the exciplex with Xe atoms is observed and its effect on spectral shifts, radiative lifetimes, and collisional deactivation are discussed. A kinetic treatment, incorporating diffusion controlled encounter probabilities, is used for the analysis of the relaxation data throughout the studied range. The radiative lifetime of the exciplex is observed to be 328(±20) ns, the exciplex is quenched by molecular chlorine with a rate constant of 7(±1)×10^-10 cm³ s^-1, while quenching by Xe is imperceptible even at the highest densities, implying a rate constant ≤10^-17 cm³ s^-1. Observations of transient loss, and their implications with respect to condensed phase triatomic rare gas halide exciplex lasers, are discussed.