Dissociative photoionization of H2 and D2 in the energy region of 25–45 eV

Dissociative photoionization of molecular hydrogen and deuterium has been studied using synchrotron radiation and an electrostatic analyzer with a position sensitive detection system for the threshold region of the doubly excited states, 25–45 eV. The Q1 1Σ+u(1) autoionizing state plays an important role in the production of fast protons below 30 eV. It is found that, for the incident photon energy 30–40 eV, the dominant process for the production of energetic protons is autoionization of the Q2 1Πu(1) state which preferentially autoionizes to the H+22pσu state rather than to the H+21sσg state. The Q2 1Πu(2) and Q2 1Σ+u autoionizing states are also found to produce fast protons in this energy region. Above 42 eV, the kinetic energy distributions are dominated by direct ionization to the 2pσu and 2pπu states of H+2.