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Scattering of Spin Polarized Positrons from Heavy Atoms: Europium and Bismuth

100%

Sharma K.

vol. 126

issue 3

688-694

We present calculations of differential, integrated elastic, total momentum transfer cross-sections and spin polarization parameters S for scattering of positron from Eu and Bi atoms in the energy range 2.0 to 500.0 eV using relativistic approach. The target projectile interaction is represented both by real and complex parameter-free optical potentials in the solution of the Dirac equation for the scattered positrons. The theoretical results are obtained from relativistic approach based on solving the Dirac equation using Hartree-Fock and Dirac-Fock wave functions to calculate cross-sections at all the energies considered.

Positron Scattering at Thermal Energies

80%

Fedus K., Karwasz G.

vol. 125

issue 3

829-832

Modified effective range theory in analytical form is used to extrapolate elastic cross-sections down to thermal energies for positron scattering from five atomic and molecular targets including Ar, H_2, N_2, C_6H_6 (benzene) and C_6H_{12} (c-hexane). The derived scattering parameters are then used to estimate the annihilation rates for chosen elements using a simple formula by Gribakin. We show that a combination of two simple models has a potential for accurate parameterization of coefficients describing the interaction of thermal positrons with non-polar targets of low polarizability such as Ar and N_2.

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2 Acta Physica Polonica A

2 2014

1 Fedus K.

1 Karwasz G.

1 Sharma K.

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Scattering of Spin Polarized Positrons from Heavy Atoms: Europium and Bismuth

Positron Scattering at Thermal Energies