Molecular frame photoelectron angular distributions in dissociative photoionization of H2 in the region of the Q1 and Q2 doubly excited states

Dissociative photoionization of H2 induced by VUV linearly polarized synchrotron radiation P has been studied using the (VH+,Ve,P) vector correlation method. The ion-electron kinetic energy correlation diagrams obtained for the three photon excitation energies hν = 20, 28.5 and 32.5 eV enable us to identify and select the dominant dissociative photoionization processes. The IΧ(θe,φe) molecular frame photoelectron angular distributions for any orientation Χ of the molecular axis with respect to the polarization are reported for direct photoionization of H2 into the H2+(2Σ+g) ionic ground state ant hν = 20 eV and for the dominant DPI processes involving autoionization of the H2(Q11Σu+(1)) and H2(Q21Πu(1)) doubly excited states into the H2+(2Σg+) and H2+(2Σu+) continua at hν = 28.5 and 32.5 eV. They show the dominant excitation of a pσu partial wave in autoionization of the Q1(1Σu+(1)) state into the H2+(1sσg) ionic state and that of a dπg partial wave in autoionization of the Q2(1Πu(1)) state into the H2+(2pσu) continuum. A molecular frame forward-backward electron emission anisotropy is observed when ionization takes place at large internuclear distance