CALCULATION OF DOUBLY-EXCITED STATES OF HELIUM WITH A FINITE DISCRETE SPECTRUM

Doubly excited states in helium are calculated with many-body perturbation theory to all orders in the electron-electron interaction. A finite and numerical basis set, rotated out into the complex plane, is used. Results, for energies and widths, are presented for states with electrons in the n = 2 and n = 3 states. The possibility of an accuracy of a few parts in 10(6) is demonstrated. The method is equally applicable to the study of doubly excited states of many-electron systems and the extension to the corresponding relativistic procedure is straightforward.