Atomic hydrogen in a strong optical radiation field

Abstract

Experimental energy spectra and energy-resolved angular distributions of photoelectrons produced by multiphoton ionization of atomic hydrogen are presented for several wavelengths bewteen 596 and 630 nm, peak intensities of about ${10}^{14}$ W/${\mathrm{cm}}^{2}$, and laser pulse durations of about 0.5 ps. Resonant ionization processes via ac Stark-shift-induced resonances with excited states dominate the spectra. The results of Sturmian-Floquet calculations of these spectra and angular distributions are presented; they are in fair agreement with the experimental data.