title: Photoinduced electron transfer and solvation in iodide-doped acetonitrile clusters.
abstract: We have used ultrafast time-resolved photoelectron imaging to measure charge transfer dynamics in iodide-doped acetonitrile clusters I(-)(CH(3)CN)(n) with n = 5-10. Strong modulations of vertical detachment energies were observed following charge transfer from the halide, allowing interpretation of the ongoing dynamics. We observe a sharp drop in the vertical detachment energy (VDE) within 300-400 fs, followed by a biexponential increase that is complete by approximately 10 ps. Comparison to theory suggests that the iodide is internally solvated and that photodetachment results in formation of a diffuse electron cloud in a confined cavity. We interpret the initial drop in VDE as a combination of expansion of the cavity and localization of the excess electron on one or two solvent molecules. The subsequent increase in VDE is attributed to a combination of the I atom leaving the cavity and rearrangement of the acetonitrile molecules to solvate the electron. The n = 5-8 clusters then show a drop in VDE of around 50 meV on a much longer time scale. The long-time VDEs are consistent with those of (CH(3)CN)(n)(-) clusters with internally solvated electrons. Although the excited-state created by the pump pulse decays by emission of a slow electron, no such decay is seen by 200 ps.
authors.affiliation: Department of Chemistry, University of California, Berkeley, 94720, USA.
authors.forename: Oli T
authors.initials: OT
authors.lastname: Ehrler
authors.forename: Graham B
authors.initials: GB
authors.lastname: Griffin
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Young
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Neumark
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D003116:Color; D004583:Electrons; D007454:Iodides / Q000737:chemistry*; D055668:Photochemical Processes; D012997:Solvents / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D000097:Acetonitriles; D007454:Iodides; D012997:Solvents; C032159:acetonitrile