Experimental energy spectra and energy-resolved angular distributions
of photoelectrons produced by multiphoton ionization of atomic hydroge
n are presented for several wavelengths between 596 and 630 nm, peak i
ntensities of about 10(14) W/CM2, and laser pulse durations of about 0
.5 ps. Resonant ionization processes via ac Stark-shift-induced resona
nces with excited states dominate the spectra. The results of Sturmian
-Floquet calculations of these spectra and angular distributions are p
resented; they are in fair agreement with the experimental data.