The Photodissociation/Recombination Dynamics of I₂ in an Ar Matrix: Wave Packet Propagation in a Mixed Quantum-Classical Picture

Abstract

The theoretical description of photodissociation processes of molecules after short time laser excitations is essentially based on the formalism of quantum mechanics, i.e. both the product formation and the energy distribution are strongly related to the time evolution of a quantum wave packet. This time evolution can be treated within fully quantum dynamical concepts with reasonable computation effort only if a very small number of degrees of freedom are considered. The situation here is very similar to that of quantum scattering theory. Only very small isolated molecules or a small number of system coordinates can be treated. Large molecules or molecules in contact with their environment are out of the scope of fully quantum dynamical calculations. In this work we present the results of a mixed quantum-classical approach wherein one relevant degree of freedom is treated quantum dynamically while all the others follow the laws of classical dynamics. The model system is a iodine molecule imbedded in a solid argon matrix. The treatment of the combined dynamics follows a discrete time-reversible propagation scheme for mixed quantum-classical dynamics which has been published recently by the present authors [1]. The results of the simulations are visualized and presented as a time sequence of images.