COLLISIONAL ENERGY-TRANSFER FROM HIGHLY VIBRATIONALLY EXCITED SF-6

Classical trajectory calculations based on the redistributed successive collision method and the single energy collision method were used to model the relaxation of vibrationally hot SF6 molecules in collisions with He, Ar, Xe, CO, and SF6. The average energy transfer is found to have a stronger than linear dependence on initial energy in SF6 for light colliders such as He, while heavier colliders such as Xe show a nonlinear increase at low energies, a linear part at intermediate energies, and a slower than linear part at high energies. The energy transfer is energy independent at high energies if the collider is SF6. The partitioning of energy transferred among vibration, rotation, and translation of the bath molecules is studied, and we find that for a CO bath, vibration is inactive, while for an SF6 bath, energy transfer to vibration accounts for most of the energy transfer. The formation of collision complexes facilitates energy transfer, but even for SF6+SF6, most of the collisions are impulsive. The relationship between these results and experiments for SF6 and other molecules is analyzed in detail, and certain common trends in energy transfer behavior are identified.