Vibrational predissociation of HF dimer in νHF=1: Influence of initially excited intermolecular vibrations on the fragmentation dynamics

Theoretical study of the influence of excited intermolecular vibrations on the total and partial decay widths of HF dimer is reported. Vibrational predissociation (VP) lifetimes and rotational state distributions of HF fragments were calculated for various quasibound states of (HF)2, corresponding to combinations of the intermolecular stretching (ν4) and bending (ν5) vibrations with the ‘‘free’’ (ν1) and ‘‘bonded’’ (ν2) HF stretch fundamentals, for total angular momentum J=1, K=0. The calculations were performed on an ab initio six-dimensional potential energy surface of Quack and Suhm, using a quantum four-dimensional golden rule methodology. The VP lifetimes and product rotational distributions exhibit pronounced dependence on the type of the initially excited intermolecular vibration of HF dimer. The energy deposited in the ν4 intermolecular stretch evolves into the translational energy of the fragments. Excitation of the ν5 intermolecular bending vibration, combined with the ν1 fundamental, is transferred to the product rotational energy. This is in good agreement with the experimental results of Bohac and Miller. We also found that in conjunction with the ν2 fundamental, most of the ν5 bending vibrational energy emerges in the translational energy of the products.