Complex coordinate studies of resonant electron-atom scattering

Abstract
Complex coordinates are used in the development of a variational principle for Siegert resonant states. The principle is first tested by application to a potential scattering problem. The position and width of the lowest 1S resonance in e-H scattering are calculated to be 9.557 eV and 0.048 eV respectively. The corresponding values for the lowest 2S resonance of He- are 19.398 eV and 0.012 eV.