Observation of laser-assisted elastic electron scattering by Ar in circularly polarized femtosecond laser fields

Abstract

Laser-assisted electron scattering (LAES) by argon atoms driven by circularly polarized femtosecond near-infrared laser fields was studied using 1 keV electrons in the single-collision regime. Energy- and angle-resolved LAES signals were recorded with an angle-resolved time-of-flight spectrometer. A direct comparison of experimental results using linear, left-circular, and right-circular polarized lasers revealed a systematic decrease in LAES intensity under circular polarization. Numerical simulations based on Mittleman’s extension of the Kroll–Watson theory reproduced the observed polarization dependence in both energy and angular distributions. No significant difference was found between left- and right-circular polarization within experimental uncertainty, in line with the theoretical prediction that the helicity-dependent contribution is negligible compared to the main term. These agreements confirm that the measured behavior is consistent with Mittleman’s theory.