Analytical transport cross section of medium energy positrons elastically scattered by complex atoms (Z=1-92)

Abstract

Transport positron-atom elastic scattering cross sections have been computed for kinetic energies in the range 500-4000 eV. The phase shifts have been calculated by numerically solving the Dirac equation for a central electrostatic field up to a large radius in which the atomic potentials are negligible. Atomic potentials were that of Hartree-Fock for Z≤18 and of Dirac-Hartree-Fock-Slater for Z≳18. An analytical expression depending on three parameters, obtained by fitting the numerical results, is proposed for the energetic range examined to calculate transport cross sections for positron-atom elastic scattering in the atomic number range 1-92. The accuracy of the given expression for energies lower than 500 eV and greater than 4000 eV has been discussed by comparison with other tabulations. © 1995 American Institute of Physics.