Precise structure calculations of 1,3Fe states of helium atom under exponentially screened Coulomb potential

The structural properties of doubly excited 1,3Fe metastable-bound and resonance states of neutral helium atom under exponentially screened Coulomb potential are studied using explicitly correlated multi-exponent Hylleraas type basis set. Precise energy eigenvalues of 2pnf(1,3Fe) states n=4−15 are estimated in the framework of Ritz variational principle. Stabilization method has been employed to calculate the resonance parameters (energy and width) of 1,3Fe states below He+(3p) and He+(4p) thresholds for different screening conditions. The resonance parameters above He+(3p) threshold under screened Coulomb environment are reported for the first time in literature. Furthermore, pioneering calculations for the variation of structural properties such as one- and two-particle moments and inter-electronic angles are carried out for both metastable-bound and resonance 1,3Fe states of He atom under screened Coulomb potential. The present results may serve as benchmark for future references.