M.T. Gning^1,, I. Sakho¹

In this paper we present accurately calculated data on the resonance parameters (resonance energy and excitation energies) of the doubly excited singlet and triplet states ^1,3S^e, ^1,3P⁰, ^1,3D^e, ^1,3F⁰ and ^1,3G^e of helium and helium-like ions (Z = 2 – 10) located below the hydrogenic thresholds N = 3 – 8, using the variational method of the Screening Constant per Unit Nuclear Charge (SCUNC) formalism. These energies are calculated using special form wave functions of the Hylleraas type and a real Hamiltonian. The results obtained are in very good agreement with the experimental and theoretical values available in the literature. The results for the energies of the doubly excited ^1,3S^e, ^1,3P⁰, ^1,3D^e, ^1,3F⁰ and ^1,3G^e states associated with hydrogenic thresholds up to N = 8 listed for the first time in this paper may provide a useful guideline for future experimental and theoretical studies in the autoionization states of two-electron systems.

helium-like systems, energy resonances, excitation energy, screening constant by unit nuclear charge (SCUNC), doubly excited states, hylleraas type wave function