Convergent close-coupling calculations of the S-wave model of positron-hydrogen scattering

The convergent close-coupling (CCC) method is extended to introduce the pos itronium formation channels. Convergence of cross-sections is studied syste matically as a function of basis types and sizes within the S-wave model of positron-hydrogen scattering. It is found that the Higgins-Burke-type reso nances disappear only if near-complete basis expansions are used for both t he atomic and positronium centers. By taking sufficiently many states withi n such calculations smooth, pseudoresonance-free cross-sections are obtaine d. (C) 2000 Elsevier Science B.V. All rights reserved.