A LASER PUMP-DISPERSED FLUORESCENCE PROBE APPROACH TO INELASTIC SCATTERING IN $S_{1}$ GLYOXAL AT VARYING COLLISION ENERGIES.

Author Institution: Department of Chemistry, Indiana UniversityA laser pump-dispersed fluorescence probe approach has been used to monitor state-to-state inelastic scattering from $S_{1} (^{a}A_{u})$ trans-glyoxal in crossed molecular beams. The trio of collision partners $H_{2}$, He, and $D_{2}$ provided the unique opportunity to explore the relative influences of the center-of-mass collision energy $(E_{cm})$ versus the interaction potential energy surface (PES). The PES for glyoxal $+ H_{2} (E_{cm} = 650cm^{-1})$ and $D_{2} (770cm^{-1})$ are identical but the relative cross sections are vastly different. In contrast, when the kinematics were matched, as in the case for glyoxal $+ He (770cm^{-1})$ and $D_{2} (770cm^{-1})$, the distribution of cross sections were nearly identical. These observations indicate that the collision kinematics dominate inelastic scattering while the details of the PES play a minor role. The experiments presented here were designed to investigate this kinematic control by selectively controlling the relative velocity and thus the center-of-mass collision energy and momentum