Intermediate energy resonance in positron-hydrogen scattering

A recent calculation by Higgins and Burke (1991), using the R-matrix method, has indicated the existence of a resonance in the positronium formation cross section in positron-hydrogen scattering. This resonance is in the J=0 partial wave at an impact energy of 35.6 eV. The authors have confirmed this observation using a similar basis set, in a momentum space formulation of the close-coupled channels approximation. They have subsequently extended the calculations to allow for some polarization of both the hydrogen and positronium. The results indicate that a resonance in the total J=0 cross section also occurs within the limits of this model, although at a different energy. Further large scale calculations are required to determine whether the resonance persists as the basis is enlarged. However it is unlikely that it could be resolved experimentally due to the presence of the higher partial waves.