Positronium formation in the n=1 and 2 states in e+-H scattering

The formation of positronium atoms in the n=1 and n=2 levels in e + -H scattering has been studied. A second Born approximation has been employed to investigate the processes. The ground-state capture cross section has also been obtained by using a model in which the second-order effect is included and the first-order term is a solution of the coupled static equation. The convergence of the second-order term has been discussed. Differential and integrated cross sections are reported in the energy range 50-1360 eV. For ground-state capture, structure in the differential cross section near the scattering angle 45' has been noticed at all energies considered. For 2s- and 2p-state capture this structure was found at and over 200 and 500 eV, respectively. The present second-order integrated cross sections are always greater than those of the first Born approximation.