Above-threshold detachment by strong ultrashort two-component laser pulses

Abstract

Detachment of electrons from negative ions by the ultrashort few-cycle laser pulses in the near-infrared spectral region is investigated using a theory based on the strong-field approximation. The differential detachment probability is computed by the numerical integration or by using the saddle-point method. The symmetry properties of the photoelectron momentum distribution are analyzed for the elliptically polarized as well as for the bi-elliptical driving field with the sine-square pulse envelope and compared with those obtained using a long pulse with a flat envelope. We show that the differential detachment probability depends, to a significant extent, on the polarization state of the driving light. For the direct electrons, i.e., the electrons which, after the detachment, do not interact with the parent atom, this is not the case if the process is induced by a long pulse with a flat envelope. In addition to the polarization state, the photoelectron momentum distribution also depends on the value of the absolute phase. We show that the qualitative and quantitative characteristics of the momentum distribution can accurately be controlled using this parameter as a control knob. This control is particularly successful in the regions where the rescattered electrons are dominant due to the fact that they stay longer in the applied laser field.