Vibrational energy redistribution across a heavy atom

Abstract

Vibrational energy relaxation is studied for a model system with two different ligands separated by a heavy atom, there being initially an excess energy in one metal-ligand subsystem. The model has eleven coordinates to achieve a high density of states (two coordinates for one metal-ligand subsystem and nine for the other). The behavior was studied using classical and quantum mechanical methods, and the results compared. Artificial intelligence searching was used in the quantum treatment, because of the large number of potentially contributing quantum states. For the present system the adiabatic separation of motion of the local group modes, previously characterized for a C-C-Sn ligand in a smaller system, still holds when the other ligand has this high density of states. Further, the agreement between the classical and quantum results is much improved over that obtained earlier for a four-coordinate symmetric system. In the latter case isolated intrinsic resonances were responsible for the “energy transfer” which was facilitated sometimes by tunneling. The present agreement of the classical and quantum calculations is generally quantitative at shorter times and at least qualitative for longer times for most states studied. This agreement is encouraging since the former can be less computationally intensive.