Quadrupole Shielding and Antishielding Factors for Several Atomic Ground States

The atomic shielding or antishielding factor R for the quadrupole hyperfine structure has been obtained for seven atomic ground states ranging from F 2p⁵ to Br 4p⁵. The values of R were determined by means of the perturbed wave functions v₁^'(nl→l^'), as obtained by solving the inhomogeneous Schr\"odinger equation for each type of excitation of the core electrons by the nuclear quadrupole moment Q. The resulting values of R have been listed, together with those for four atomic states which had been previously investigated. For the atomic ground states in this region of the Periodic Table, R is generally positive (shielding), and of the order of +0.1, except for Al $3p$ and Ga $4p$, for which R is negative, because of the antishielding provided by the 2p→p and 3p→p perturbations, respectively. The resulting correction factors C=1(1-R) have been applied to the quadrupole moments of 11 nuclear isotopes. We have also obtained the ionic antishielding factor γ_∞ for the Sc³⁺ ion, γ_∞(Sc³⁺)-11.2.