A crossed-beam study of the state-resolved dynamics of CH( X sup 2. Pi. )+D sub 2. I. The inelastic scattering channel

The state-to-state integral cross sections for the inelastic scattering of CH({ital X} {sup 2}{Pi}) and D{sub 2} to produce rotationally excited CH({ital X} {sup 2}{Pi}) product have been measured in a crossed-beam apparatus by the laser-induced fluorescence method. Two types of measurements were performed: (1) the translational energy dependence of an individual quantum state of the product and (2) the state distribution of the products at fixed and well-defined translational energy. For the inelastic scattering channel, the cross sections gradually increased from a dynamical threshold to a broad maximum and then slowly decreased as the translational energy increases. Evidence for multiple-impact rotational rainbows was found and a possible frequency-locking phenomenon between the two receding rotors resulted. Moderate orbital alignment was observed except for the highest rotational levels of the product. By comparing and contrasting the kinematically similar system CH({ital X} {sup 2}{Pi})+He, the influence of a strongly attractive potential energy surface on the inelastic scattering of CH+D{sub 2} was inferred. Combining the results of the inelastic scattering and the isotopic exchange channels (the following paper) provide an unprecedented look into the dynamics of collisions between CH({ital X} {sup 2}{Pi}) and D{sub 2}.