Autoionizing 1Σu+ and 1Πu states of H2 above the third and fourth ionization thresholds

We report calculations of energy positions, autoionization widths and branching ratios for the (1)Sigma (+)(u) and (1)Pi (u) doubly excited states of H-2 lying above the (2)Pi (u)(2p pi (u)) and (2)Sigma (+)(g)(2s sigma (g)) ionization thresholds. The resonance parameters have been obtained using the Feshbach theory and an L-2 representation of the non-resonant continuum with B-spline functions. Our theoretical predictions may be of interest in interpreting recent photoabsorption experiments.