Interference in the angular distribution of photoelectrons in superimposed XUV and optical laser fields

Abstract

The angular distribution of photoelectrons ejected during the ionization of Ne atoms by extreme ultraviolet (XUV) free-electron laser radiation in the presence of an intense near infrared (NIR) dressing field were investigated experimentally and theoretically. The highly nonlinear process with absorption and emission of more than 10 NIR photons results in the formation of numerous sidebands. The intensity of the sidebands varies strongly with the emission angle and the angular distribution pattern reveals clear signatures of interferences between the different angular momenta for the outgoing electron in the multi-photon process. As a specific feature, the central photoelectron line is characterized at highest NIR fields by an angular distribution,