Sternheimer valence shielding and antishielding factors for several 2p and 3p atoms and ions

The Sternheimer valence shielding and antishielding factor R has been calculated for the isoelectronic series of atoms in 2p<SUP>1</SUP>, 2p<SUP>2</SUP>, 2p<SUP>4</SUP>, 2p<SUP>5</SUP>, 3p<SUP>1</SUP>, 3p<SUP>4</SUP>, and 3p<SUP>5</SUP> electronic configurations by means of the uncoupled numerical Hartree-Fock method. A slightly larger shielding effect is observed for the <SUP>1</SUP>D state relative to the <SUP>3</SUP>P state for N<SUP>−</SUP>, O, and S. In the 2p<SUP>4</SUP> series, where N<SUP>−</SUP> is included, it is found that the mononegative ion is characterized by an R which is twice as large as that for the isoelectronic neutral atom. The general trends observed in the variation of R within an isoelectronic series are discussed