Polarised density approach to atomic collisions. Scattering of positrons from atomic hydrogen and the noble gases

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Abstract
The polarised orbital method for the adiabatic description of low-energy electron/positron-atom scattering is reformulated in terms of a polarised density. The polarised density is expanded into multipoles and the radial functions are treated variationally. This procedure is shown to provide an accurate dipole polarisation potential for e+/e--H scattering. For many-electron targets the quantum statistical Thomas-Fermi energy functional with gradient corrections is used to calculate dipole and quadrupole polarisation potentials. Total elastic cross sections for positron energies below excitation thresholds agree with experiment and with polarised orbital Hartree-Fock calculations for e+-Ne scattering, while the agreement is less satisfactory for e+-Ar scattering.