Vibrational predissociation dynamics and internal rotation in aromatic van der Waals complexes

Abstract

The Vibrational Predissociation (VP) lifetimes and dissociation channels are reported for the van der Waals complexes p-DiFluoroBenzene-Ar (pDFB-Ar), pDFB-N2 and p-FluoroToluene-Ar (pFT-Ar). The dissociation occurs on theS1 potential energy surface after excitation of an S1 ring breathing level with evib ≈ 800 cm−1. Trends are observed in the lifetimes and dissociation channels as the experiments move among the complexes. The VP characteristics of pFT-Ar are most distinctive. As opposed to all other aromatic complexes, pFT-Ar has little VP channel selectivity. These complexes are members of a set chosen to explore the VP vibrational dynamics by systematic changes of complex level structure. The change from pDFB-Ar to pDFB-N2 introduces nearly free internal rotation in the complex partner and an additional van der Waals mode. pFT-Ar introduces a nearly free internal rotation attached directly to the ring. We discuss how these changes may be related to the observed VP dynamics.