Excitations of H2 by positron impact

Abstract

In this paper, we present a theoretical study of scattering cross sections for positron impact of electronic states of hydrogen molecule (H₂) using the scaling Born positron (SBP) approach. Cross sections to low-lying electronic states, B¹∑⁺_u, C¹П_u, B´¹ ∑⁺_u, and D¹П_u are investigated. In an earlier theoretical effort [J.L.S.Lino, Rev. Mex. Fisica 62 (2016) 596], an application of the SBP approach for the X¹∑⁺_g - > B¹∑⁺_u electronic excitation of the H₂ molecule, gave cross sections with reasonable qualitative agreement with experimental data [J.P.Sullivan et. al., Phys.Rev.Lett.87,073201 (2001)]. However, recent studies for the excitation of the B¹∑⁺_u state by positron impact showed that this electronic state still demand of a refined degree of description of the quality of the cross sections (Weiss et. al., Eur. Phys. J. D (2018) 72). The purpose of this work was to reexamine the B¹∑⁺_u state and verify the quality of the numerical convergence of SBP method and extend the investigation to other states. The possibility to estimate a indirect contribution of multichannel effects ( three states considering the ground X¹, B¹∑⁺_u and E,F¹∑⁺_u state) are introduced within the SBP context. For the first time, integral cross sections to these new states using the SBP approach are reported. In the absence of the experimental data and theoretical developments, comparisons are made with analogous electron scattering.