AC stark shifts in 3+2 photoionization with a pulsed, stochastic field

We have computationally investigated AC stark shifts in 3 + 2 photoionization with a pulsed, stochastic field, The purpose of these studies was to elucidate the effect on observed AC Stark shifts of the interplay between stochastic and (deterministic) spatio-temporal laser field variations. For a spatially uniform field, we find that there are ''resonance-like'' increases in the AC Stark shift modification factor, Re[M], when it is considered as a function of the pulsed laser intensity. One of these resonances is shown to correlate with a change in the 3-photon transition's Bloch-vector trajectory entropy, suggesting that the dynamical character of the S-photon transition during a laser pulse can have an important influence on observed AC Stark shifts, For fields with a gaussian spatial distribution the resonance-like features are less pronounced. These results indicate that evaluations of Re[M], and hence the extraction of AC Stark shift coefficients from experimental data, should not only account for the stochastic characteristics of a field, but also concomitant (deterministic) spatio-temporal field variations.