Spectroscopy and Relaxation Kinetics of Matrix-Isolated CH/D Radicals

Abstract

The A2Δ−X2Π and B2Σ-−X2Π transitions of CH/D were examined for radicals trapped in Ar and Kr matrixes. Excitation spectra yield further evidence that CH/D(B) rotates in solid Ar and Kr. Vibrational relaxation of CH/D(B) is faster for the heavier isotope, indicating that vibration to rotation energy transfer is the dominant mechanism. The decay of CH(B), v = 0 is primarily radiative in both Ar and Kr, with small contributions from B → A nonradiative transfer. Fluorescence was not detected from CD(B), v = 0 as the B → A transfer process was much faster than radiative decay for this isotope. The proximity of the CD(B), v = 0 and (A), v = 1 levels is responsible for the accelerated transfer rate. Spectra for the A−X transition of CH−Arn clusters were recorded for comparison with the matrix data. Relative to free CH, the transition is blue-shifted in the cluster and red-shifted in an Ar matrix. This contrast suggests that the clusters consist of CH bound to the surface of Arn.