CALCULATION OF RESONANCES IN DOUBLY-EXCITED HELIUM USING THE STABILIZATION METHOD

Mandelshtam, Ravuri, and Taylor [Phys. Rev. Lett. 70, 1932 (1993)] have recently proposed a novel approach for the calculation of resonance states in one- and two-channel problems. We show that a modification of this approach, suitable for stabilization calculations, can yield both the resonance position and width for doubly excited states in two-electron systems. This provides a simple and numerically efficient method to calculate the spectral density of states. In the region of overlapping 1S(e) Rydberg manifolds, we find very narrow resonances associated with the symmetric excitation of both electrons. The mechanism for the occurrence of such resonances is discussed.