Photopreparation of molecular hydrogen ions in intense laser fields

Detailed experiments on the energy and angular distributions of both electr ons and protons formed from molecular hydrogen in strong femtosecond laser fields are reported. At the wavelengths 389 and 406 nm the ionization dynam ics is governed by resonance shifting of molecular Rydberg states. Differen ces from this mechanism appear only at the very lowest intensities, when cl ose lying resonances of the E, F-state determine the photoelectron pattern in resonant enhanced ionization, and at very high intensities, when tunnel ionization suppresses molecular details. At wavelengths below 400 nm at int ensities in the range of approximate to 10.3 W/cm(2) femtosecond pulses are quite suitable for preparation of state selected H-2(+) targets in a restr icted range of vibrational levels.