Systematics of moments of dipole oscillator-strength distribution for members of the He isoelectronic sequence

Abstract

An analytic representation for the oscillator-strength sums S( k) for members of the He isoelectronic sequence is proposed. The expression holds for both positive and negative values of k. The values of the moments S( k) exhibit an interesting Z-dependence, where Z is the nuclear charge. This, together with some observations on H - and the mass polarization effect, are discussed.