Solving close-coupling equations in momentum space without singularities

Solving the close-coupling equations for electron–atom scattering in momentum space involves the solution of coupled integral equations, which contain principal value singularities. These can be accurately treated numerically using an on-shell subtraction technique. Here we show how the singularities may be taken into account analytically, leading to an alternative approach to the solution of the integral equations. The robustness of the method is demonstrated by considering the S-wave model of e-H scattering across eight orders of magnitude of incident energies