2p n p ( 1,3 P e ) states of neutral He and Li + ions under Debye plasma screening

The energy eigenvalues of doubly excited 2p n p ( 1 P e ) ( n = 3–8) and 2p n p ( 3 P e ) ( n = 2–7) bound states of a neutral helium atom and singly ionized lithium atom are estimated under weakly coupled plasma screening for the first time using an explicitly correlated Hylleraas-type basis in the framework of the Rayleigh–Ritz variational principle. The Debye screening model has been employed to include the effect of plasma background. Improvement over the existing approximated theoretical results has been achieved for the above-mentioned states of neutral helium under Debye plasma screening. The modified energy eigenvalues of 1,3 P e states arising from two p electrons of a Li + ion in the Debye plasma environment are being reported for the first time.