Positronium-hydrogen-atom scattering in a five-state model

Abstract

The scattering of orthopositronium (Ps) by hydrogen atoms has been investigated in a five-state coupled-channel model allowing for Ps(1s)H(2s,2p) and Ps(2s,2p)H(1s) excitations using a recently proposed electron-exchange model potential. The higher (n≥3) excitations and ionization of the Ps atom are calculated using the first Born approximation. Calculations are reported of scattering lengths, phase shifts, elastic, Ps and H excitation, and total cross sections. Remarkable correlations are observed between the S-wave Ps-H binding energy and the singlet scattering length, effective range, and resonance energy obtained in various model calculations. These correlations suggest that if a Ps-H dynamical model yields the correct result for one of these four observables, it is expected to lead to the correct result for the other three. The present model, which is constructed so as to reproduce the Ps-H resonance at 4.01 eV, automatically yields a Ps-H bound state at -1.05 eV that compares well with the accurate value of -1.067 eV. The model leads to a singlet scattering length of 3.72a0 and effective range of 1.67a0, whereas the correlations suggest the precise values of 3.50a0 and 1.65a 0 for these observables, respectively. © 1999 The American Physical Society.