Photoelectron-photofragment coincidence spectroscopy of the dissociative photodetachment of I2- at 258 and 266 nm

Abstract

Photoelectron-photofragment coincidence (PPC) spectroscopy is used to examine the dissociative photodetachment (DPD) of at 266 and 258 nm in a kinematically complete manner. The resonance enhancement of predissociation in the DPD of is reported for the first time and a previously reported shift to a low KER channel at high photon energy is ascribed to vibrationally excited anions [K.E. Kautzman, P.E. Crider, D.E. Szpunar and D.M. Neumark, J. Phys. Chem. A 111 (49), 12795–12801 (2007)]. Photodetachment to the bound X and A states of results in stable , whereas excitation to a repulsive state results in dissociation of , forming two ground state I atoms. DPD occurs via multiple energetically accessible repulsive states, both directly and via predissociation of the bound state of . At 266 nm direct DPD and resonance enhanced predissociation dominate the DPD dynamics, whereas at 258 nm predissociation is less favoured and direct DPD shifts to preferentially occur via the state, particularly for vibrationally excited anions. Bound-continuum Franck–Condon factors are calculated to model the individual contributions to the dissociative photoelectron spectra from three energetically accessible repulsive states.