Relaxation dynamics of photoexcited benzene–rare gas van der Waals complexes

Publisher Website
Google Scholar
Abstract
The vibrational relaxation/predissociation dynamics of various benzene–rare gas van der Waals complexes have been investigated. These studies indicate that the pathways of vibrational redistribution within the complex are highly selective and involve only a small subset of the energetically accessible levels. While in general energy gap law behavior is observed, i.e., large benzene vibrational energy changes are disfavored, the sensitivity of the relaxation dynamics to this constraint varies with the vibrational level initially excited. This behavior is ascribed to varying degrees of sensitivity to the details of the atom–molecule potential and is related to the scheme of nuclear displacements involved in the benzene normal modes. Some, but not all, of the relaxation dynamics can be understood in terms of a very simple model that expresses the atom–molecule potential as a sum of atom–atom interactions and assumes a rigid geometry for the complex. A kinetic analysis that assumes only first order processes allows crude vibrational relaxation‐predissociation rate constants to be extracted. The variation of the rate constants with rare gas and vibrational level is consistent with the energy gap law.