Nuclear Dynamics of Benzene···(Ar)n Clusters

Abstract

In this paper we report on constant energy molecular dynamics (MD) simulations of nuclear dynamics of benzene−Ar and benzene−Arn (n = 2−7) clusters, utilizing the ab initio intermolecular potential of benzene−Ar. The dissociation dynamics of benzene−Ar resulting from a nonselective excitation of the intermolecular modes exhibits an excess energy dependence which can be accounted for in terms of the Rice−Ramsperger−Kassel−Marcus (RRKM) statistical theory. The time-resolved isomerization dynamics of benzeneAr2 and rigid nonrigid isomerization of benzene−Arn (n = 2−7) was investigated. The intracluster vibrational energy redistribution (ICVR) in benzene−Ar from an intramolecular vibration to the intermolecular modes is inefficient on the nanosecond time scale for all of the (one quantum or two quanta) vibrational excitation of each mode. The mode selectivity of the ICVR and its linear dependence on the excess vibrational energy were established. The vibrational predissociation (VP) times for single-mode excitations of benzene−Ar are also slow on the nanosecond time scale (>22 ns), in accord with experimental data. The retardation of ICVR and VP of benzene−Ar reflects the bottleneck effect for intracluster vibrational energy flow, due to the considerable frequency mismatch between the high-frequency vibrational modes of benzene (ω = 402−2955 cm-1) and the low-frequency van der Waals vibrational modes (ω = 26 and 40 cm-1).