Scattering of near-zero-energy electrons and positrons byH2

Abstract

The parameters for $S$-wave elastic scattering of near-zero-energy electrons and positrons by ${H}_{2}$ molecules are calculated using the stabilization method with explicitly correlated Gaussians. The confined variational method is applied to optimize the Gaussians to describe the short-range interaction of incident ${e}^{\ifmmode\pm\else\textpm\fi{}}$ with ${H}_{2}$ in the fixed-nuclei approximation. For ${e}^{+}$-${H}_{2}$ scattering the scattering length of previous work [Phys. Rev. Lett. 103, 223202 (2009)] is substantially improved. More importantly, for ${e}^{\ensuremath{-}}$-${H}_{2}$ scattering, from first principles, the scattering length is computed as a function of the internuclear distance. In the case that the two nuclei are at the equilibrium distance the results are in a good agreement with values derived from fitting experimental total and diffusion cross sections to the modified effective range theory.