Low-energy S-wave Positronium-Hydrogen Collisions

In response to proposed measurements discussed by St.~Olaf's positron group of low-energy positronium-alkali atom scattering [1], we begun a theoretical investigation of Ps scattering. Recently, we computed singlet and triplet S-wave phase shifts for low-energy elastic Ps-H scattering process. This process is of interest since it is a fundamental four-body Coulomb process. We employed the Kohn variational method and a number of variants on the method, namely, the inverse Kohn, generalized Kohn, and the complex Kohn for the S-matrix and T-matrix. We compare our results to the earlier Kohn and inverse Kohn calculations [2,3]. \\[4pt] [1] Jason Engbrecht, {\it Private Communication}.\\[0pt] [2] P.~Van Reeth and J.~W.~Humberston, J.~Phys.~B {\bf 36}, 1923 (2003).\\[0pt] [3] P.~Van Reeth and J.~W.~Humberston, Nucl.~Instrum.~Methods Phys.~Res. A {\bf 221},140 (2004).