Perturbation-wave packet studies of vibrational predissociation in collinear X–BC van der Waals complexes: He⋅⋅⋅I2(B 3Π)

Abstract

A time‐dependent wave packet method for the investigation of adiabatic vibrational predissociation (VP) of collinear X–BC systems is described. Discrete–discrete and discrete–continuum couplings are introduced into the initial wave function using a first‐order perturbation procedure. The system wave packet is evolved in time by an explicit integration procedure and reaction probabilities P(t) as a function of time are computed by integrating the wave packet over the configuration space of the VP products. The VP rate coefficient is given directly by {−∂ ln[1−P(t)]/∂t}. The method has been applied to the vibrational predissociation of He–I₂ (B ³Π). Zero and first‐order VP rate coefficients and decay half‐widths have been computed as a function of initial I₂ vibrational state and X‐atom mass for both pairwise harmonic and Morse potentials. Comparisons with previously reported distorted wave and quasiclassical trajectory calculations and with measured VP rates show all the methods to be of similar accuracy.