Calculation of above threshold ionization with elliptically polarized light.

We present a calculation of the rate and angular dependence for ionization above threshold by intense laser radiation, and compare the results to recent Nd:YAG experiments in xenon and krypton.(1) The calculation is performed for arbitrary laser polarization, and considers temporal and spatial inhomogeneities in the laser focus, as well as final state ponderomotive effects. (2,3) The ionization calculation is non-perturbative in the electromagnetic interaction. It is exact only if the laser field interaction commutes with the atomic hamiltonian, which is not true in the case of interest. Thus this must be viewed as an approximation, valid when the commutator is small. The predictions for circular or linear polarization are similar to those of Reiss.(4,5) This is the first attempt to extend such calculations to the experimentally interesting case of optical polarization, and the resulting predictions are in striking agreement withe experiment.