Schwinger variational principle for electron-molecule scattering: Application to electron-hydrogen scattering

The authors report the first application of the Schwinger variational principle to electron-molecule scattering. Results for electron-${\mathrm{H}}_2$ scattering in the static-exchange approximation show that the Schwinger method can provide accurate solutions of the scattering problem with small descrete basis sets. The Schwinger variational expression is found to converge far more quickly with respect to the size of the basis than any other algebraic expansion technique considered to date. Results are also presented for hybrid trial scattering wave functions containing both continuum and discrete basis functions.