Complex-basis-function Floquet calculations of multiphoton ionization rates in hydrogen systems

Abstract

We use the complex-basis-function technique to calculate one- and two-photon photoionization rates in intense light sources for atomic hydrogen, the hydrogen negative ion and the hydrogen molecular ion. For H2+ we also calculate three-photon ionization rates. Rather than calculating the ionization rates in the perturbation approximation, we take account of strong field effects by calculating complex quasienergies using a mixture of real and complex-basis functions. This allows us to extend the calculations from the perturbative to the non-perturbative regime as the laser intensity is increased. The method works well and gives reliable estimates of these rates.