Simplification of photoelectron spectra of H2 in intense laser fields

The response of molecular hydrogen to multiphoton excitation with intense short laser pulses is probed using photoelectron spectroscopy. At wavelengths and laser intensities for which molecular Rydberg states are ac Stark shifted into resonance, the small quantum defects of molecular hydrogen and the loss of the ponderomotive energy to the electromagnetic field give rise to very simple photoelectron spectra that coincide with those of excited atomic hydrogen. (Author)