Configuration-interaction calculations of positron binding to zinc and cadmium

The configuration-interaction method is applied to the study of positronic zinc (e+Zn) and positronic cadmium (e+Cd). The estimated binding energies and annihilation rates were 0.00373 hartree and 0.42×109 sec-1 for e+Zn and 0.006 10 hartree and 0.56×109 sec-1 for e+Cd. The low-energy elastic cross section and Zeff were estimated from a model potential that was tuned to the binding energies and annihilation rates. Since the scattering lengths were positive (14.5a0 for Zn and 11.6a0 for Cd) the differential cross sections are larger at backward angles than at forward angles just above threshold. The possibilities of measuring differential cross sections to confirm positron binding to these atoms is discussed

Calculation of positron-electron enhancement factors for real metals on a base of band structure data

We have developed a method based on Bethe-Goldstone equation for calculation k- dependent positron-electron enhancement factors. In the method, the electron and positron band structure wavefunctions, densities and energies are used and the e•-e- effective potential depends locally on positron position in a cell. The integral equation is solved approximately by a special linearization and the integration over the first Brillouin zone is carried out using Rath-Freeman tetrahedron scheme. The resulting k-, r- , G-, and band dependent wavefunctions are used to calculate enhancement factors for bee and fee metals. The preliminary results are discussed and compared with ones found experimentally and theoretically by other authors