Dynamics of nonadiabatic reactions (theory). II. Product vibrational excitation

Abstract

The same model potentials as were used in part I (preceding paper) have been employed in a study of the effect of nonadiabatic exchange reaction on product vibrational energy distributions. The exit-valley seam at which hopping from a lower (L) to an upper (U) potential energy surface (pes) occurred could be altered from early (E) to late (L), and from inner (I) to outer (O). The splitting 2ε, between the pes could be made small or large. The computations involved trajectory surface hopping for the mass-combination light plus heavy light (L+HL), in three dimensions (3D). The effects on P(v′) of alterations in reagent energy, and changes in the pes, could be understood in terms of the local motion, part way through the reactive encounter in the configurations at which the seam was encountered. The seam was effective as a ‘‘filter’’ favoring reaction into low v′U′, , following the hop to the upper pes, particularly if ε was large, since the seam allowed trajectories with higher speed along the exit valley to pass onto the U surface and these correlated with low vU. Surface hopping strongly favored low v′U if the seam location was of the ‘‘inner’’ type (I), and favored high vU if the seam was an ‘‘outer’’ one (O), since the reaction intermediate leading to the upper surface was a compressed one in the former case, and an extended one in the latter.