Observing electron-correlation features in two-photon double ionization of helium

Abstract

By numerically solving the time-dependent Schr\odinger equation for helium in its full dimensionality, we determine the joint momentum spectrum along the polarization direction $P({k}_{1z},{k}_{2z})$ for two-photon double ionization (TPDI). We identify features uniquely attributable to dynamical correlation effects in the double continuum. We show that some of the correlation signatures persist in integrated measures, in particular the emission asymmetry, that should become accessible with upcoming XUV light sources. We also compare with predictions of analytic models for TPDI which neglect such final-state correlations.