Basis-set calculation of Siegert eigenvalues: Partial resonance widths

Abstract

The calculation of complex resonance eigenvalues for electron-atom and electron-molecule scattering by discrete-basis-set methods yields total resonance widths directly. The authors show that, as a consequence of the separable nature of the $S$ matrix near a resonance, discrete-basis-set methods may also be used to compute partial widths for resonances in a multichannel problem. The procedure is applied to a model three-channel problem to demonstrate its numerical effectiveness.