NUCLEAR-DYNAMICS OF BENZENE(CENTER-DOT-CENTER-DOT-CENTER-DOT)(AR)(N) CLUSTERS

In this paper we report on constant energy molecular dynamics (MD) sim ulations of nuclear dynamics of benzene-Ar and benzene-Ar-n (n = 2-7) clusters, utilizing the ab initio intermolecular potential of benzene- Ar. The dissociation dynamics of benzene-Ar resulting from a nonselect ive excitation of the intermolecular modes exhibits an excess energy d ependence which can be accounted for in terms of the Rice-Ramsperger-K assel-Marcus (RRKM) statistical theory. The time-resolved isomerizatio n dynamics of benzene-Ar-2 and rigid nonrigid isomerization of benzene -Ar, (n = 2-7) was investigated. The intracluster vibrational energy r edistribution (ICVR) in benzene-Ar from an intramolecular vibration to the intermolecular modes is inefficient on the nanosecond time scale for all of the tone quantum or two quanta) vibrational excitation of e ach mode. The mode selectivity of the ICVR and its linear dependence o n the excess vibrational energy were established. The vibrational pred issociation (VP) times for single-mode excitations of benzene-Ar are a lso slow on the nanosecond time scale (>22 ns), in accord with experim ental 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 vibrationa l modes of benzene (omega = 402-2955 cm(-1)) and the low-frequency van der Waals vibrational modes (omega = 26 and 40 cm(-1)).