Elastic positron scattering by calcium atom in optical potential approach

Full text: The results of optical potential (OP) approach calculations of phaseshifts, partial, differential and total cross sections for elastic positron scattering by calcium atoms at 0-500 eV collision energy are presented. For OP the approximations are used from the simple static to more complex static-polarization with absorption approximation. The positron-atom polarization interaction potential is taken in the non-parametric (non-adjustable) form [1] and has a dipole-quadrupole asymptotic behaviour. The static potential and the electron density of target atom required for OP-components are analytically expressed via the parameters obtained by approximating the above characteristics calculated in the local approximation of the density functional theory. An absorption potential, similarly to electron scattering, is used within the free electron gas approximation with the correction made for the exchange exclusion [2]. Scattering phase shifts are sought by using a variable phase method. Calculated positron scattering cross sections are compared to the available data and to those obtained in the similar approach describing electron scattering. Special attention is drown to the low (<10 eV) and high (200-500 eV) collision energy range