PHOTODISSOCIATION AND METASTABLE DECAY OF SOLVATED CLUSTER IONS

The stepwise solvation of dissociative ions was studied using a new technique in which a time-of-flight mass spectrometer is operated as a tunable low mass rejection filter. Two studies reflecting different modes of operation are reported. (1) Electronically excited aniline cation C6H 3NH2+ was produced by picosecond photoionization and the rate of metastable dissociation to C5H 6+ + HNC was investigated as a function stepwise solvation by NH3. The addition of just one or two NH3 solvent molecules was found to significantly reduce the rate of dissociation relative to the bare ion at comparable ion energies. (2) The resonant photodissociation of (CH3I)n+ cluster ions, formed by electron impact (EI) ionization, was investigated in a crossed electron-laser-molecular beam configuration. No evidence for C-I dissociation, which is prominent in the bare ion, was observed. Instead van der Waals dissociation occurred by one- and two-photon mechanisms that varied depending on cluster size. © 1990 American Institute of Physics.