High-Intensity Photoionization of H sub 2

A tunable, high-intensity picosecond dye laser system has been employed with electron energy analysis to investigate the dynamics of (3+1) resonance-enhanced multiphoton ionization of H2 via different vibrational levels of its electronic states. We observe production of molecular ions in various vibrational levels, with a shift to increased population of lower vibrational states of H2(+) consistent with the a.c. Stark shift of the correspondingly lower vibrational levels of the C state into resonance with the three-photon energy of the laser. Clear evidence of direct dissociation of H2 followed by single-photon ionization of the excited H atom is observed as well. Above threshold ionization of these two processes occurs readily. We also find that dissociative ionization is an increasingly important ionization pathway, which we assign to photoionization into a transient bound state created by the avoided crossing of the first repulsive electronic state of H2(+), with the single-photon dressed ground state of H2(+). This article is from 'Osa Proceedings of the Topical Meeting (5th) on Short-Wave Length Coherent Radiation: Generation and Applications Held in Monterey, California o 8-10 April 1991. Volume 11,' AD-A252 973, p227-231.