Regular Article

Positron scattering by the Ar₂ and Xe₂ dimers^⋆

Departamento de Física, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil

^a e-mail: e.p.seidel@posgrad.ufsc.br

Received: 30 September 2019
Received in final form: 14 December 2019
Published online: 20 February 2020

Abstract

Positron scattering by Ar₂ and Xe₂ dimers are studied for low incident energies. The Zero Range Potential approximation is used and the dimer is modeled as two independent atoms under an internuclear distance constraint. The scattering calculations are performed within the fixed nuclei and the rigid rotor formulations. For the fixed nuclei approximation, analytical expressions are obtained for the positron-dimer scattering length and for the elastic cross section. In the rigid rotor treatment, an analytical expression is obtained for the rotational excitation cross sections. The main results obtained in this investigation are that the short-range interaction between the positron and the molecular dimer is the dominant mechanism for rotational excitation in this energy range. Such effect is explained by the small values of the quadrupole moments of the Ar₂ and Xe₂ dimers.