Positron scattering by the Ar2 and Xe2 dimers

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.