Adiabatic-nuclei calculations of positron scattering from molecular hydrogen

Abstract

The single-center adiabatic-nuclei convergent close-coupling method is used to investigate positron collisions with molecular hydrogen (${\mathrm{H}}_{2}$) in the ground and first vibrationally excited states. Cross sections are presented over the energy range from 1 to 1000 eV for elastic scattering, vibrational excitation, total ionization, and the grand total cross section. The present adiabatic-nuclei positron-${\mathrm{H}}_{2}$ scattering length is calculated as $A=\ensuremath{-}2.70{a}_{0}$ for the ground state and $A=\ensuremath{-}3.16{a}_{0}$ for the first vibrationally excited state. The present elastic differential cross sections are also used to ``correct'' the low-energy grand total cross-section measurements of the Trento group [A. Zecca et al., Phys. Rev. A 80, 032702 (2009)] for the forward-angle-scattering effect. In general, the comparison with experiment is good. By performing convergence studies, we estimate that our ${R}_{m}=1.448{a}_{0}$ fixed-nuclei results are converged to within $\ifmmode\pm\else\textpm\fi{}5%$ for the major scattering integrated cross sections.