Time shifts in photoemission from a fully correlated two-electron model system

We theoretically investigate time-resolved photoemission originating from two different shells (1s and 2p) of a fully correlated atomic two-electron model system ionized by an extreme-ultraviolet attosecond light pulse. The parameters of the model system are tuned such that the ionization potentials of the 1s and 2p electrons have values close to those of the 2s and 2p levels in a neon atom, for which a relative time delay has been measured in a recent attosecond streaking experiment by Schultze et al. [Science 328, 1658 (2010)]. Up to now theoretical efforts could account only for delays more than a factor of 2 shorter than the reported experimental value. By solving the time-dependent Schrodinger equation numerically exactly we explore the influence of correlations on the time delay previously implicated as one of the potential sources of discrepancies. We investigate the influence of the interplay between electron interactions and the probing streaking infrared field on the extracted relative delays between the two emission channels. We find that for our model system the inclusion of electronic correlation only slightly modifies the time shifts, as compared to a mean-field treatment. In particular, the correlation-induced time delay is contained in the Eisenbud-Wigner-Smith time delay for the photoionization process.