  We investigated the two-dimensional electron momentum distributions of atomic
negative ions in an intense laser field by solving the time-dependent
Schrodinger equation (TDSE) and using the first- and 2nd-order strong-field
approximations (SFA). We showed that photoelectron energy distributions and
low-energy photoelectron momentum spectra predicted from SFA are in reasonable
agreement with the solutions from the TDSE. More importantly, we showed that
accurate electron-atom elastic scattering cross sections can be retrieved
directly from high-energy electron momentum spectra of atomic negative ions in
the laser field. This opens up the possibility of measuring electron-atom and
electron-molecule scattering cross sections from the photodetachment of atomic
and molecular negative ions by intense short lasers, respectively, with
temporal resolutions in the order of femtoseconds.
