The Binding Energy of PsH

In response to proposed measurements of Ps scattering by the St.~Olaf's positron experimental group [1], we have begun a theoretical investigation of Ps scattering from simple atoms. For our first step of this investigation, we have computed the binding energy of the fundamental four-body Coulomb system, PsH. We have used a very flexible trial function of Hylleraas form which includes all inter-particle distances. Our most accurate value of the binding energy compares favorably with a previous calculation that also used Hylleraas functions [2] and with the most accurate calculation to-date which used explicitly correlated Gaussians [3]. \\[4pt] [1] Jason Engbrecht, {\it Private communication}, (2008).\\[0pt] [2] Zong-Chao Yan and Y.~K.~Ho, Phys.~Rev.~A {\bf 59}, 2697 (1999).\\[0pt] [3] Sergiy Bubin and Ludwik Adamowicz, Phys.~Rev.~A {\bf 74}, 052502 (2006).