OPTICAL-POTENTIAL METHOD WITH CAPTURE CHANNEL IN POSITRON ATOM SCATTERING

A tractable optical potential method in which the Ps formation channel is included explicitly is developed for positron-atom scattering using an integral approach in momentum space. The method is suitable at medium energies. A model calculation is carried out using four eigenstates (H(1s) and Ps(1s) in P space and H(2s) and H(2p) in Q space) and the results are found to be in good agreement with four-eigenstate CCA calculations at medium energies. A three-state (H(1s, 2s, 2p)) optical potential calculation has also been performed and it shows that the effect of the Ps formation channel on the direct channel is significant even at an incident energy of 100 eV.