The close-coupling method for electron/positronatom scattering promises to give a complete description of the scattering process provided the space of target states is properly spanned. This paper will discuss the structure of the equations, emphasising questions of stability associated with the expansions over sets of target states. For electronatom scattering, the character of the solution is discussed and a simple example is given to illustrate the non-convergence of the half-shell T-matrix. This lack of convergence can be fixed by application of the symmetrisation boundary condition, leading to new forms of the equations. For positronatom scattering, the standard equations yield convergent half-shell T-matrices for all but the largest calculations.
Close-coupling Formalism for Electron/PositronAtom Systems and Underlying Scattering Theory
