DOUBLY-EXCITED STATES IN THE SPECTRUM OF MOLECULAR-HYDROGEN

An ab initio calculation of the fixed-nuclei scattering information re quired for multichannel quantum defect applications is presented for s everal symmetries of molecular hydrogen. This represents a modest step toward the longer-range goal of constructing a unified theoretical de scription of all fragmentation channels in H-2, including ionization a nd both neutral and ionic dissociation channels. The errors in our cal culated fixed-nuclei quantum defects are generally in the range 0.005- 0.05. This is sufficiently accurate to consider a fully ab initio calc ulation of H-2 photoabsorption near the ionization threshold, includin g rovibrational channel interactions by the usual frame transformation method.