Doubly excited 1,3Po resonances of helium below the N=2-9 ionisation thresholds

A novel approach is used to evaluate energies of singlet and triplet resonance states of helium below the N=2-9 hydrogenic thresholds. We have combined the variational method with the no-linear parameters of Hylleraas and the β-parameters of screening constant by unit nuclear charge. Comparison with various available theoretical and experimental literature values indicates a good agreement.