The photodetachment of a model one-electron ion simulating ${\mathrm{H}}^{\mathrm{-}}$ in the presence of a low-frequency field is analyzed. Two different geometries are considered in order to get information on the effect of the ponderomotive energy shift Δ on the photodetachment cross section. Our calculations suggest that a correspondence may be established between the ponderomotive shift and the photodetachment cross section, when the ejected electron may exchange only a few low-frequency photons. This is in qualitative agreement with recent experimental observations. When a large number of processes are open in which the detached electron may exchange low-frequency photons with comparable probability, it is impossible to make any connection between ponderomotive threshold shift and photodetachment cross section which, instead, may be described in terms of a field picture.

• Received 22 July 1991

DOI:https://doi.org/10.1103/PhysRevA.45.3268