Intramolecular Energy Transfer and Mode-Specific Effects in UnimolecularReactions of Disilane

摘要

Intramolecular energy transfer rates and pathways in disilane Si2H6 have beeninvestigated in detail by analysis of the envelope functions of the time variation of the uncoupled normal-mode kinetic energies and by a new method that involves the Fourier transform of the local-mode bond energies. The results show that the total intramolecular vibrational relaxation (IVR) rate out of a given mode is generally much faster than the total dissociation rate. However, many of the individual mode-to-mode rate coefficients are significantly smaller than this rate. Consequently, IVR is not globally rapid on the time scale of the reactions. The Si-Si and local modes relax over a much longer time scale than the Si-H modes. This observed decoupling of sets of internal modes is interpreted to mean that phase space is not explored ergodically on the time scale of the reactions, even at internal energies significantly greater than the dissociation thresholds. Reprints