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Physical Review A

Calculation of spin-polarized positronium-helium (2 S3) and electron-helium (2 S3) scattering

Yi Zhang, M.-S. Wu, Ying Qian, Kálmán Varga, Jun-Yi Zhang

Published May 5, 2021• 5 citations
Publisher

Abstract

Low-energy properties of spin-polarized electron-helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ and spin-polarized positronium-helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ scattering are calculated using the modified confined variational method. To take the van der Waals interaction into consideration, the van der Waals coefficient between positronium and helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ is calculated using the explicitly correlated Gaussian basis. Compared with the ground state noble gases, the larger scattering length and zero pickoff annihilation rate indicates that $\mathrm{He}(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ may be a more suitable cooling gas. In the energy range we considered, no similarity is found for the $S$-wave cross sections between these two scatterings. A Ramsauer-Townsend minimum is observed in spin-polarized electron-helium$(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ scattering due to the large polarization of metastable helium. This may open a new way to find and study the Ramsauer-Townsend effect.

DOI
10.1103/physreva.103.052803

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Total cross sections for the scattering of low-energy electrons and positrons by atomic beryllium in the energy range below the first inelastic thresholds are calculated. A Ramsauer–Townsend minimum is seen in the electron scattering cross sections, while no such effect is found in the case of positron scattering. A minimum total cross section of 0.016 a 0 2 at 0.0029 eV is observed for the electron case. In the limit of zero energy, the cross sections yield a scattering length of −0.61 a 0 for electron and a 0 for positron scattering.
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