A time-dependent calculation for vibrational predissociation of H2HF

Abstract

Calculations of the total and partial decay widths are presented for the vibrational predissociation of H2HF. The calculation is done for the total angular momentum J=0 of the molecule and for the dissociation process H2HF(v=1)→H2(v=0)+HF(v=0). A time-dependent golden rule wave packet method is employed in the numerical calculation for the decay widths. The lifetime of the complex is determined from our calculation to be about 600 ns for para- and 1600 ns for ortho-H2HF. These values are much larger than the experimentally measured value of 27 ns for ortho-H2HF. The large discrepancy in lifetime for H2HF is in sharp contrast to the excellent agreement in lifetime for D2HF between theory and experiment, though the same potential energy surface is used in both calculations. We also present the rotational state distribution of the fragments H2 and HF following the vibrational predissociation of H2HF. It is found that about 58% of the final rotational population is in j=4 states of H2 for para-H2HF and about 48% is in j=5 states of H2 for ortho-H2HF.