Ionization potentials and electron affinites for a spacially nondegenerate doublet state in a second-order electron propagator approach

The identification of poles in approximate electron propagator calculations on open shell systems has been analyzed. The electron propagator consistent through second order in electronic repulsion has been derived for a 2Σ reference state. Calculations are performed on Li, Na, and BeH and the accuracy of the result is comparable to the one obtained for closed shell systems.