The complex potential-energy function for nuclear motion in the Born-Oppenheimer approximation for the lowest ${}_{}{}^2{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ resonance state of ${\mathrm{H}}_2^{-}$ has been calculated using the complex self-consistent-field (CSCF) method which treats the incident and target electrons equivalently. There is substantial disagreement among various determinations of the complex potential function for the broad ${}_{}{}^2{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ resonance. The CSCF results agree best with the potential used by Bardsley and Wadehra [Phys. Rev. Lett. 41, 1795 (1978)] to compute dissociative attachment cross sections. The calculated width of the resonance as a function of internuclear distance is in excellent agreement with the form used by Bardsley and Wadehra while the real part of the CSCF potential agrees less well with their function. It is suggested that correlation effects are important in determining the position of the resonance and in determining the width at least near the internuclear distance at which the resonance becomes a bound state.

• Received 1 December 1981

DOI:https://doi.org/10.1103/PhysRevA.25.2529