Abstract
We analyze energy spectra of photoelectrons ejected by strong laser pulses, using the manifestly gauge-invariant approach. Gauge-invariant expressions for the ionization amplitude can be obtained by grouping together all terms of the same order in atomic potential in the standard strong-field approximation (SFA) expansion. We calculate energy spectra of photoelectrons for the hydrogen atom, and compare them with results based on numerical solutions of the time-dependent Schrödinger equation. Agreement, at least qualitative, is observed for an electric-field amplitude higher than 1 a.u., and for larger energies of ionized electrons, basically beyond the region, where the standard SFA is usually applied.
- Received 21 October 2012
DOI:https://doi.org/10.1103/PhysRevA.87.025402
©2013 American Physical Society