PHOTOCHEMISTRY OF NAPHTHALENE CLUSTER IONS (C10H8)(N)(-7 - FORMATION OF C11H9+ ION VIA INTERVALENCE BAND EXCITATION(), N=2)

The photodissociation dynamics of naphthalene cluster ions, (C10H8)(n) (+) with n = 2-7, in the visible and near-IR wavelength regions have b een probed by photoionization-photofragmentation time-of-flight mass s pectroscopy. An intracluster reaction leading to production of a C11H9 + ion is observed when the parent cluster ions are excited with near-I R photons, while only intramolecular fragmentation pathways occur foll owing visible band excitation. The formation of C11H9+, which is assum ed to possess the benzotropylium structure, is ascribed to a photochem ical rearrangement of the dimer ion core produced in the parent cluste rs upon multiphoton excitation via the intervalence transition band. T he intracluster reaction is observed only for parent cluster sizes n g reater than or equal to 4, which suggests that the dimer ion core must be surrounded by a solvent cage involving at least two neutral molecu les. We propose that the existence of a dimer core structure plays an important role in the photochemistry that occurs subsequent to excitat ion into the intervalence transition band.