Streaking induced finite-range time delays*

We theoretically study time delays for photoionization in a streaking experiment by numerically solving the time-dependent Schr\"odinger equation. Our results show that the time delay in the numerical simulations is solely induced by the coupling between the streaking field and the atomic potential, and can be well approximated by a classical approach. The analysis implies that the time delay is related to a finite range in space, over which the emitted electron propagates during the interaction with the streaking field along its polarization direction. We also demonstrate that, for a short-range potential, in certain limiting cases the streaking induced finite-range time delay approaches the Wigner-Smith time delay.