The photodetachment spectrum of OHF-:: the influence of vibration at a transition state

New ab initio potential energy functions for collinear OHF- and OHF have been used with time-dependent wavepacket studies in a simulation of the photodetachment spectrum of the OHF- anion. Franck-Condon excitation of OHF- lies within the transition state region for the bimolecular reaction F + OH <-> O + HF on the lowest triplet surface. The branching ratios for fragmentation of the excited OHF are such that the peaks in this spectrum may each be correlated with dissociation to a single vibrational state of the O + HF(v) or OH(v) + F products. The possible influence of vibrational excitation of the anion has been explored also. This is predicted to lead to marked changes in the spectra. Experimental observations of such spectra could be used in refinement of the potential as could an experiment in which the electron kinetic energy is detected in coincidence with the vibrational states of the molecular products or with the kinetic energy of the atomic products. The calculations revealed a number of metastable resonances on the OHF surface, although these are all at higher energies than are relevant to the photodetachment spectrum from the ground state anion.