Spectrum and vibrational predissociation of the HF dimer. II. Photodissociation cross sections and product state distributions

Abstract

We study vibrational predissociation of the HF dimer both by a full coupled channels treatment as well as in the Fermi golden rule approximation. Photodissociation cross sections, linewidths, and rotational state distributions are computed for excitations from the ground state with rotational quantum numbers J=1, K=0 to monomer stretch excited states with J=K=0, both for even and odd permutation symmetry. The resonances investigated include excitation of the hydrogen bond donor and acceptor stretches, as well as combinations of one of these modes with the dimer stretch and dimer geared-bending modes. We find that dissociation is sufficiently slow for the Fermi golden rule approximation to be valid. The resonance positions and line strengths are compared with quasibound state calculations. The agreement with experimental data is fairly good for the photofragment angular distributions that were determined from the rotational state distributions, less good for some of the linewidths. Since we carefully checked that the results are converged with respect to the number of vibrational and rotational channels included, the remaining discrepancies are almost certainly due to small deficiencies in the SO-3 potential used in the calculations.