Three-dimensional quantum dynamics study of vibrational predissociation of HeI2 van der Waals molecule for low vibrational excitation using the time-dependent wave packet method

Abstract

Three-dimensional quantum mechanical calculations for vibrational predissociation of He12(B) van der Waals molecules are presented using the time-dependent wave packet technique within the golden rule approximation. The total and partial decay widths, lifetimes, rates and their dependence on initial vibrational states were obtained for HeI2 at low initial vibrational excited levels. Our calculations show that the calculated total decay widths, lifetimes and rates agree well with those extrapolated from experimental data available. The predicted total decay widths as a function of initial vibrational states exhibit highly nonlinear behavior. The very short propagation time (less than 1 ps) required in the golden rule wave packet calculation is determined by the duration time of the final state interaction between the fragments on the vibrationally deexcited adiabatic potential surface. The final state interaction between the fragments is shown to play an important role in determining the final rotational distribution. This interpretation clearly explains the dynamical effect that the final rotational distribution shifts to the lower rotational energy levels as the initial vibrational quantum numberu increases.