A novel estimate of the two-photon double-ionization cross section of helium

In a previous publication, a procedure was proposed for unambiguously extracting the cross sections for double ionization and single ionization from a time-propagated wavepacket, and it was tested on the well-known case of one-photon double ionization of helium successfully. Here, we apply it to the two-photon process for which the numerically predicted double ionization cross section is not completely stabilized yet. Our results confirm the value obtained for this cross section by all but two active groups in the field, they definitely exonerate electron correlations in the final state from any responsibility in this splitting of the published data into two sets, they emphasize the need for a more careful account of reflection effects and propose a tentative explanation for an overestimation of the cross section in the J-matrix method. They also demonstrate the conceptual and computational advantages of the method proposed. (Some figures may appear in colour only in the online journal)