Feshbach-model potential approach for the study of resonant and bound states of Be-like ions

We present an implementaion of the Feshbach formalism to calculate energy positions and widths of doubly excited states of Be-like ions. These systems can be treated formally as two-electron problems by using a suitable model potential to describe the effect of the 1s² core. In this respect, we discuss the pertinence of using the one-parameter model potential Vₘ=2r^-1-2r^-1(1+{α}r)e^-2αr. Energies and widths for 1s²4l4l' ¹{S}ᵉ$ and $¹Pᵒ autoionizing states of N³⁺ and Ne⁶⁺ are reported.