A TIME-INDEPENDENT THEORY OF PHOTODISSOCIATION BASED ON POLYNOMIAL PROPAGATION

The time-dependent quantum theory of molecular photodissociation of He ller is reformulated in the framework of polynomial propagation. The n ew formulation retains the essential features of the time-dependent ap proach, but requires neither propagation in time nor interpolation of the evolution operator. In this new approach, the propagation is carri ed out by recursion of the corresponding orthogonal polynomial, which requires minimal storage. The wave packet can be restricted to real sp ace, further reducing cpu and memory requirements. If the wave packet is propagated by the Chebyshev operator, the total cross section can b e obtained via the cosine Fourier transform from the order-dependent a utocorrelation function. Like the time-dependent approach, the interna l state distributions of the fragment can be projected out from the as ymptotic wave packet. The nonadiabatic photodissociation of methyl iod ide with two active dimensions is employed to illustrate the applicabi lity of the new approach. (C) 1998 American Institute of Physics.