MASS-SELECTIVE IONIZATION-DETECTED STIMULATED RAMAN-SPECTROSCOPY OF BENZENE TRIMER AND HIGHER CLUSTERS

We present the results of mass-selective, ionization-detected stimulat ed Raman spectroscopies on jet-cooled benzene clusters from the trimer to the octamer. The data pertain to the fundamentals of the totally s ymmetric ring-breathing (nu1) and C-H stretch (nu2) modes of benzene a nd provide information about geometrical structure and vibrational dyn amics. For the trimer, the results indicate a species in which all thr ee benzenes reside in equivalent sites. For the higher clusters the re sults point to geometries involving two or more inequivalent sites. Th e nu1-excited trimer is found to decay on a nanosecond, or longer, tim e scale. The nu2-excited trimer decays on a time scale of greater than 5 ps. Similar timescales characterize the decays of the nu2-excited t etramer and pentamer.