Two-electron excited states and adiabatic quantum defects ofH2: Analysis of elastic scattering of electrons fromH2+

The spheroidal $s\sigma$-, $p\sigma$-, $p\pi$-, and $d\sigma$-wave phase shifts for the scattering of electrons from ${\mathrm{H}}_2^{+}$ 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 ${}_{}{}^1{}_{}{}^{}\Sigma _g^{}{}_{}{}^{}$, ${}_{}{}^{1,3}{}_{}{}^{}\Sigma _u^{}{}_{}{}^{}$, and ${}_{}{}^{1,3}{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$. 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.