Pseudochannel approach to scattering problems: The calculation of coupling elements from ground-state expectation values

We derive and test a new method for replacing an infinite set of close-coupling equations with only two equations, of the same form but involving an effective coupling potential. The resulting coupling matrix element is entirely expressible in terms of ground-state expectation values. As an example, we test the new method for a model system of electron--hydrogen-atom scattering and find that the calculations involving only ground-state properties do predict results in good agreement with calculations in which excited states are included explicitly.