Vibrational Relaxation of Matrix-Isolated CH sub 3 F and HCl

摘要

Kinetic and spectroscopic studies have been performed on CH sub 3 F and HCl as a function of host matrix and temperature. Temporally and spectrally resolved infrared fluorescence was used to monitor the populations of both the initially excited state and the lower lying levels which participate in the relaxation process. For CH sub 3 F, relaxation from any of the levels near 3.5 mu , i.e. the CH stretching fundamentals or bend overtones, occurs via rapid (< 5 ns) V implies V transfer to 2 nu sub 3 with subsequent relaxation of the nu sub 3 (CF stretch) manifold. Lifetimes of 2 nu sub 3 and nu sub 3 were determined through overtone, delta V = 2, and fundamental fluorescence. These lifetimes show a dramatic dependence on host lattice, an increase of two orders of magnitude in going from Xe and Ar matrices. Lifetimes depend only weakly on temperature. The relaxation of 2 nu sub 3 and nu sub 3 is consistent with a model in which production of a highly rotationally excited guest via collisions with the repulsive wall of the host is the rate limiting step. For HCl, lifetimes of v = 1,2,3 have been determined. In all hosts, the relaxation is non-radiative. For a given vibrational state, v, the relaxation rate increases in the series k(Ar) < k(Kr) < k(Xe). The dependence of the relaxation rate; on v is superlinear in all matrices, the deviation from linearity increasng in the order Ar < Kr < Xe. The relaxation rates become more strongly temperature dependent with increasing vibrational excitation. The results are consistent with a mechanism in which complex formation introduces the anisotropy necessary to induce a near resonant V implies R transition in the rate limiting step. (ERA citation 07:044908)