Core polarization corrections to oscillator strengths in the alkali atoms

Abstract

The polarization of the core of an alkali atom by the residual interaction with the valence electron which Hartree-Fock theory ignores should lead to a slight positive hole near the valence electron. This should reduce the oscillator strengths of low-lying transitions of the valence electron, where this electron is sufficiently close to the core to polarize it strongly. The physical picture is verified, and the magnitude of the effect calculated by treating the residual interaction as a perturbation. The reduction found in the oscillator strength of the lowest ns -> np transition of the valence electron increases from less than 1% in lithium to 16% in caesium.