Diabatic potential curves for symmetric doubly-excited 1Se states: the isoelectronic sequence

Abstract

The description of symmetric doubly-excited states of two-electron ions as eigenstates of a diabatic potential for interelectronic motion is extended to the whole two-electron isoelectronic sequence. The authors' calculated energies of infinite series of intrashell states of 1Se symmetry are fitted to a universal double-Rydberg formula for the complete isoelectronic sequence. The underlying dynamics in the formation of such states is shown to be the stabilising influence of rapid interelectronic vibration on the inherently unstable motion of the electronic centre-of-mass around the saddle point of the three-body potential.