Factors controlling the competition among rotational and vibrational energy transfer channels in glyoxal

Abstract

The state-to-state transfer of rotational and vibrational energy has been studied for S ₁ glyoxal (CHOCHO) in collisions with D₂, N₂, CO and C₂H₄ using crossed molecular beams. A laser is used to pump glyoxal seeded in He to its S ₁ zero point level with zero angular momentum about its top axis (K′ = 0). The inelastic scattering to each of at least 26 S ₁ glyoxal rotational and rovibrational levels is monitored by dispersed S ₁–S ₀ fluorescence. Various collision partners are chosen to investigate the relative influences of reduced mass and the collision pair interaction potential on the competition among the energy transfer channels. When the data are combined with that obtained previously from other collision partners whose masses range from 2 to 84 amu, it is seen that the channel competition is controlled primarily by the kinematics of the collisional interaction. Variations in the intermolecular potential play strictly a secondary role.