Dissociative autoionization in (1+2)-photon above-threshold excitation of H2 molecules

We have studied theoretically the effect of dissociative autoionization on the photoelectron energy spectrum in (1+2)-photon above-threshold ionization (ATI) of H2 molecules. We have considered excitation from the ground Xg1Σ+(ν=0,j) state to the doubly excited autoionizing states of u1Σ+ and u1Π symmetry, via the intermediate resonant Bu1Σ+(ν=5,j) states. We have shown that the photoelectron energy spectrum is oscillatory in nature and shows three distinct peaks above the photoelectron energy 0.7 eV. This feature has been observed in a recent experiment by Rottke et al (1997 J. Phys. B: At. Mol. Opt. Phys. 30 4049). (author)