Auto-Ionization in Doubly Excited Helium and theλ320.4andλ357.5Lines

Abstract

The probabilities of auto-ionization of the $2s^2{}_{}{}^1{}_{}{}^{}S$, $2s2p{}_{}{}^3{}_{}{}^{}P$, $2p^2{}_{}{}^1{}_{}{}^{}D$, $3d^2{}_{}{}^1{}_{}{}^{}G$ states of He are calculated with continuous wave functions which are obtained by numerical integration of the wave equation including the effect of exchange. The probabilities are 4×${10}^{14}$, 5×${10}^{13}$, 1×${10}^{14}$, 4.9×${10}^{13}$ per second, respectively, for these states. On the basis of these calculations and the theoretical energies of the doubly excited states, the identification of the two lines $\lambda 320.4$ and $\lambda 357.5$ observed by Compton and Boyce and by Kruger is discussed. The former has been reasonably definitely ascribed to the transition $1s2p{}_{}{}^3{}_{}{}^{}P-2\mathrm{}{p}^2{}_{}{}^3{}_{}{}^{}P$, the state $2p^2{}_{}{}^3{}_{}{}^{}P$ not being subject to auto-ionization. The latter line cannot be satisfactorily accounted for with respect to both the position and the width of the line.