Quantum mechanical computational studies of chemical reactions : III. Collinear A + BC reaction with some model potential energy surfaces

Abstract

The effects of the location of the energy barrier and of changing vibrational frequency along the reaction path on the reaction dynamics of a collinear A + BC → AB + C reaction were studied using a series of ‘diagnostic’ model potential energy surfaces. In accord with the classical trajectory study, vibration was found markedly more effective than translation in promoting reaction on a surface with a barrier located at the exit valley, and vice versa on a surface with a barrier placed in the entry valley. Considerable vibrational population inversion in the reaction product was found for an ‘early-down-hill’-type surface with a barrier placed in the entry valley. The energy release was exceedingly speecific, particularly so for the F + H₂/F + D₂ collinear collision on a realistic surface. Resonances in reactive molecular collisions were evident whenever the static effect of changing vibrational frequency along the reaction path gave rise to the potential wells necessary to support these quasibound states.