Determination of cross sections and continuum phases of rubidium through complete measurements of atomic multiphoton ionization

We present a complete experimental determination of the atomic parameters necessary to unambiguously characterize two-photon ionization of atomic rubidium, i.e., the relative photoionization cross sections and the continuum wave function phase difference. We obtain these complete results through a single measurement, that of the two-photon photoelectron angular distribution using elliptically polarized light. While measured phase differences are in excellent agreement with expected values, the ratios of photoionization cross sections of the two D channels are not.