Off-shell effects in laser-assisted scattering

Within the impulse approximation for laser-assisted electron-potential scattering we discuss the effects of off-energy-shell propagation, describing the electron-potential scattering by a solvable analytical model. Off-shell effects are shown to be present for long-range potentials in the regime where the exchange of photons is classically forbidden, but are expected to be small under experimental conditions realized so far In contrast, in the regime where the exchange of photons is classically allowed, the impulse approximation reduces to the on-shell version of the Kroll-Watson theory and off-shell effects are, accordingly, absent.