2-PHOTON DISSOCIATIVE PHOTOIONIZATION AND PHOTODISSOCIATION OF SINGLEH2B (1)SIGMA(+)(U)(NU=5) ROTATIONAL STATES

We report on an experimental study of dissociative photoionization and neutral dissociation of H-2 by two-photon excitation from single B (1 ) Sigma(u)(+)(v = 5) rotational states (photon energy approximate to 4 eV). The B-state rovibrational levels are excited in the same light p ulse by three-photon absorption from X (1) Sigma(g)(+)(v = 0). Angle r esolved photoelectron and ion kinetic energy distributions allow us to discriminate between the different decay channels. Neutral decay is d etected by one-photon ionization of excited atomic hydrogen product st ates. The kinetic energy distribution of photoelectrons from dissociat ive photoionization shows an oscillatory structure which depends on th e initial B-state rotational quantum number J. An indication of a corr esponding structure in the ion kinetic energy distributions is only fo und for J = 0. similar to results reported by Verschuur et al we find neutral decay preferentially into high principal quantum number atomic states. The results indicate that the H-2 Q(1) doubly excited states play a crucial role in the decay processes.