Resonances and exchange in the scattering of electrons by helium atoms II. Correlated helium wave function

Abstract

The elastic scattering of electrons by helium atoms is calculated with a target wave function containing some correlation. Polarization is simulated by the addition of a small attractive potential. A resonance is found at an energy which is extremely sensitive to the magnitude of the polarization. The resonant wave function has one electron in the 1s level, and the other two in the correlation component (orthogonal to (1s)²) of the helium ground state. The treatment shows that such a resonance should always be found in a one-channel calculation with a target wave function containing some correlation. However, the customary approximations are of such dubious validity at the resonance that it is doubtful whether anything like it exists in the real world.