Population transfer between degenerate continuum states via impulsive stimulated Raman scattering: application to the control of HOD photofragmentation

This work proposes a new scheme for the coherent control of the branching ratio of photodissociation reactions. HOD's photodissociation in the first electronic-excited state illustrates the idea. The scheme involves the induction of quantum interference between the continuum eigenstates of the excited state through interaction with a non-resonant NIR ultrashort laser pulse, subsequent to electronic excitation. A high-level, frequency-dependent excited state polarizability surface of HOD is determined, in order to model the non-resonant coupling between the laser pulse and molecule. The results of this scheme on the control of the branching ratio between OD + H and OH + D are presented, as well as an analysis of the interaction between the ultrashort pulses and the excited-state eigenstates. The understanding of the degenerate nature of these continuum states is shown to be crucial for a correct description of the processes that lead to a change in the reaction's outcome, and is further discussed through an exploration of a model system.