STATE-TO-STATE INELASTIC-SCATTERING FROM S-1 GLYOXAL WITH THE RARE-GAS SERIES - UNIFORM ROTATIONAL VS CHANGING VIBRATIONAL CHANNEL COMPETITION

To provide data for the complete series of rare gases, relative cross sections are obtained for the crossed molecular beam state-to-state ro tationally and rovibrationally inelastic scattering of S-1 ((1)A(u)) g lyoxal (CHO-CHO) in its 0 degrees, K' = 0 states by Ne, Ar, and Xe. Wh en added to cross sections from a new analysis of Kr data and to publi shed data for Hz and He, sets of cross sections for the entire rare ga s series are available that show the competition among more than 25 ro tational and rovibrational channels. The latter all involve Delta upsi lon(7)' = +1 where v(7)' = 233 cm(-1) is the lowest frequency mode. De spite large variations in the collisional kinematics and in the intera ction potential energy surfaces, the competition among rotationally in elastic channels is essentially identical for the gases Ne, Ar, Kr, an d Xe. In turn, those cases differ from H-2 and He solely by the fact t hat orbital angular momentum constraints with the light gases limit sc attering to only those states with Delta K less than or similar to 15. In contrast, the competition between rotational and rovibrational sca ttering changes with the collision partner to the extent that state-to -state resolution of rovibrational scattering is not possible for Ar, Kr, and Xe. Previous theoretical predictions for Ar inelastic scatteri ng are consistent with earlier arguments that this competition is domi nated by kinematic factors rather than by variations in the interactio n potential. The relative cross sections are obtained from experiments in which a laser prepares St glyoxal in the 0 degrees K' = 0 state wi th J' approximate to 0-10. Dispersed S-1-S-0 fluorescence is used to m onitor the inelastic scattering to more than 25 destination states wit h Delta K' resolution. Inelastic cross sections are extracted by compu ter simulation of the fluorescence spectra.