Abstract

Doubly excited atoms, with two excited electrons, occur both above and below the first ionization limit. The interactions between the doubly excited states and the energetically similar singly excited channels are manifested by autoionization and series perturbations in these two cases. Historically these states have been studied by ultraviolet photo-absorption from the ground state. The absorption of the doubly excited state can be thought of as originating in the small excited state admixture of the ground state. This absorption is neccessarily weak with the result that it is comparable to direct photoionization. As both the excitation to the autoionizing state and the excitation to the continuum lead to an ion and an electron these two processes interfere to produce the familiar Beutler Fano profile characteristic of autoionizing states.

© 1986 Optical Society of America