Near threshold photodetachment of electrons from negative ions and its dependence on the shape of the laser pulse envelope

Abstract

Near threshold photodetachment of electrons from negative ions is investigated theoretically. Various profiles of the laser pulse time envelope f(t) are considered. The Stark shift ( delta E 0 ) max of the ground level E 0 is assumed to be large mod ( delta E 0 ) max mod tau >>1, where tau is the pulse duration. The saturation regime found earlier is shown to be realisable rigorously only in the case of the exponential envelope f 0 (t)=exp(- mod t mod / tau ). For any other f(t) deviations from the saturation are shown to be larger the more significantly f(t) deviates from f 0 (t). In the case of the Gaussian curve f(t) the photodetachment probability w depends only slowly (logarithmically) on the peak field strength E 0 . The function w(E 0 ) is shown to depend not only of f(t) but also on the detuning from the threshold Delta . For some model functions f(t) the dependence w(E 0 ) is found analytically for all Delta , mod Delta mod <or approximately= mod ( delta E 0 ) max mod . For large positive Delta the photodetachment probability is found for any envelope f(t).