Two-electron excited states and adiabatic quantum defects of H/sub 2/: Analysis of elastic scattering of electrons from H/sub 2/ /sup +/

The spheroidal ssigma-, psigma-, p..pi..-, and dsigma-wave phase shifts for the scattering of electrons from H/sub 2/ /sup +/ are calculated at various internuclear distances by the Kohn variational method in the prolate-spheroidal coordinate system. The positions and widths of the two-electron excited resonance states are obtained for the symmetries /sup 1/..sigma../sub g/, /sup 1,3/..sigma../sub u/, and /sup 1,3/Pi/sub u/. Adiabatic quantum defects are also obtained by extrapolating the phase shifts to the low-energy limit. Importance of these quantities is discussed briefly in connection with the study of various dynamic processes of highly excited states of molecules.