EXCITED-STATE VIBRATIONAL DYNAMICS OF 4-ETHYLANILINE (X)1 CLUSTERS (X=AR, N-2, AND CH-4)

Intracluster vibrational redistribution (IVR) and vibrational predissociation (VP) dynamics of 4-ethylaniline (Ar)1, (N2)1, and (CH4)1 clusters have been studied by time-correlated single photon counting, mass-resolved excitation spectroscopy, and dispersed emission spectroscopy. The 4-ethylaniline molecule has a low frequency ethyl group torsion vibrational mode, which is similar in energy to the van der Waals modes of the clusters. This mode, because of its low energy (approximately 35 cm-1), plays a role in the vibrational dynamics of the clusters studied. The cluster dissociation rates and product state distributions can be modeled by a serial IVR/VP mechanism for which the VP step is treated by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The resulting agreement between the calculated and experimental rates and product state intensities indicates that a statistical distribution of energy among all low frequency modes exists for 4-ethylaniline/polyatomic solvent clusters in which k(IVR) much greater than k(VP). For 4-ethylaniline (Ar)1 clusters k(VP) > k(IVR) and a statistical distribution of energy among the chromophore and van der Waals modes is not achieved. The central determining factor for the vibrational dynamics of these clusters is overall density of low energy modes.