Vibrational mode and collision energy effects on a highly constrained reaction: OCS+(ν)+OCS→CS+2+CO2 and S+2+2 CO

Abstract

We report the effects of collision energy and OCS+ vibrational state (ν1, ν2, and ν3) on the reaction of OCS+ with OCS. Production of CS+2+CO2 is exoergic and the cross section shows no evidence of an activation barrier. Nonetheless, the cross section is only ∼0.1% of the collision cross section, even at low collision energies where formation of an intermediate complex is facile. There appears to be a severe phase-space (steric) bottleneck for this rearrangement reaction. CS+2 production is weakly inhibited by collision energy, and enhanced by all three modes of OCS+ reactant vibrational excitation. Production of S+2 is endoergic and is enhanced by collision energy and by ν2 (bend) and ν3 (CS stretch) excitation. Excitation of ν1 (CO stretch) does not enhance this channel, even though it is the highest energy mode. At high collision energies, S+2 production becomes relatively efficient, suggesting that the reaction mechanism for this channel is direct with no significant bottleneck.