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

Abstract

The structural properties of doubly excited ${}^{1,3}{F}^e$ 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 $2pnf\left({}^{1,3}{F}^e\right)$ states $\left(n=4-15\right)$ are estimated in the framework of Ritz variational principle. Stabilization method has been employed to calculate the resonance parameters (energy and width) of ${}^{1,3}{F}^e$ states below $H{e}^{+}\left(3p\right)$ and $H{e}^{+}\left(4p\right)$ thresholds for different screening conditions. The resonance parameters above $H{e}^{+}\left(3p\right)$ 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 ${}^{1,3}{F}^e$ states of He atom under screened Coulomb potential. The present results may serve as benchmark for future references.