Angular aspects of electron correlation and the Coulomb hole. II. The 2 ¹S and the 2 ³S excited states of helium

The K-L intershell correlation effects for both singlet and triplet states arising from the 1s2s electronic configuration of the helium atom are analyzed in detail with the aid of the complete (nonreduced) interelectronic probability density and the local Coulomb hole functions. The calculations for both singlet and triplet states suggest the existence of nuclear Coulomb well channels similar to those recently described for the intrashell case of Berry and Krause. When the reference electron is close to the nucleus, the 2 ¹S Coulomb hole resembles the ground state Coulomb hole, whereas this feature is lost in the 2 ³S state due to the effect of exchange correlation. Electron correlation is shown to reduce the nuclear shielding provided by the K-shell distribution and, as a consequence, to lead to a relative shrinking of the outer shell density. Other differences between the ground state and excited state correlation effects are described.