Theoretical Atomic Collisions Laboratory

The zero-energy Born exchange amplitude for electron-helium scattering in the forward direction has been calculated using a multi-parameter Hylleraas-type wavefunction. Up to 125 terms are used and the result is extrapolated to be 3.9430+or-0.0016. The present calculation substantiates the conclusion reached in several recent papers that the zero-energy form of the Gerjuoy-Krall dispersion relation (1960, 1962) does not hold for e - -He scattering.