Probing Electron Correlation via Attosecond XUV Pulses in the Two-Photon   Double Ionization of Helium
  Recent experimental developments of high-intensity, short-pulse XUV light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called "sequential" regime (photon energy above 54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow to induce and probe angular and energy correlations of the emitted electrons. The final momentum distribution reveals regions dominated by the Wannier ridge break-up scenario and by post-collision interaction. 
J. Feist, S. Nagele, R. Pazourek, E. Persson, B. I. Schneider, L. A.   Collins, J. Burgd\"orfer