Nonperturbative wave packet dynamics of the photodissociation of H2+ in ultrashort laser pulses

Abstract

The wave packet dynamics of the photodissociation of H2+ under excitation by laser pulses of short durations at 329.7 nm are studied. The photodissociation process involves essentially two coupled channels, and the detailed mechanism for the formation of fragment kinetic energy spectra is examined by following the evolution of structures in the coupled-channel wave functions in momentum space. These structures appear in the channels’ momentum wave functions at P≠0, as the v=0 ground vibrational state is promoted to the dissociative channel then accelerated. The variations of these structures reflect the interplay between local laser-induced transitions and the accelerating–decelerating action of intrinsic molecular forces. The wave packet dynamics are studied for rectangular and Gaussian pulses of varying durations and peak intensities. In addition, two forms of channel couplings were considered corresponding to two different choices of the gauge: the electric-field (EF) gauge, in which the matter–field interaction is of the length form and the radiation-field (RF) gauge, in which it is of the velocity form.