Scattering theory of photodissociation in strong laser fields: photon induced predissociation in IBr

Theory of photodissociation in a strong laser field is developed in a systematic way. Photon absorption and molecular dissociation are treated uniformally using time-dependent quantum scattering theory. The connection between the physically realizable situation, in which a multimode coherent pulse dissociates a molecule and the computationally convenient occupation number representation, is made in a very explicit way. The coherence (or incoherence) of the radiation field and that of the wave packet of scattering states generated by it are shown to be linked together in a very straightforward fashion. The analytic properties of the scattering wave functions and the existence and duration of off-the-energy-shell transients are shown to be connected. The theory is applied to studying the laser assisted dissociation, in a two color experiment, of IBr. The role of two-photon absorption vs photon catalyzed dissociation is investigated.