Minimum-variance approach to electron-scattering calculations: Elimination of anomalies and Monte Carlo implementation

It is demonstrated, in calculations on one- and two-electron systems, that K-matrix (real-valued) boundary conditions in the trial wave function in the minimum-variance method can give anomalies at certain energies, while T-matrix (complex) boundary conditions do not. A Monte Carlo procedure is proposed for computing scattering amplitudes in a many-electron system that uses the minimum-variance approach to treat incident and target electrons on the same footing. Successful exploratory calculations on e/sup -/-H scattering in the radial limit suggest that this approach may provide a path to direct Monte Carlo scattering calculations on many-fermion systems