Crossed beam rovibrational energy transfer from st glyoxal. 2. uniform scattering characteristics from the initial levels 00, 51, and 81
Abstract
Results are reported for an extension to higher initial states of crossed molecular beam inelastic scattering from 1Au trans-glyoxal (CHOCHO) by He collisions with 95-meV (770-cm-1) center-of-mass collision energy. A laser pump prepares glyoxal in the initial level v5′ = 509 cm-1 or vg′ = 735 cm-1 with high rotational selectivity about the top axis; K′ = 0 for v5′ and K′ = 0-3 for vg′. A dispersed fluorescence probe detects the final states of rotationally and of rovibrationally inelastic scattering with resolution of ΔK transitions. Semiquantitative relative cross sections are obtained for the state-to-state scattering. The rovibrational channels show the same extreme selectivity that is observed for scattering from lower levels. Only a single quantum change in the lowest frequency mode, the CHO-CHO torsion vΓ′ = 233 cm-1, may be securely assigned. Scattering to much closer vibrational levels is not competitive. The state-resolved inelastic scattering characteristics of the three levels 00, 51, and 81 are now seen to be identical to within experimental uncertainty. The similarity involves both the competition between the rotational and rovibrational scattering channels as seen in the relative cross sections and the distribution of cross sections for the various ΔK processes within these channels. The experimental results are in agreement with the three-dimensional quantal scattering predictions of Kroes, Rettschnick, and Clary. © 1994 American Chemical Society.