Rigorous lower-bound $p$ -wave positron-hydrogen phase shifts are calculated below the positronium pick-up threshold. The wave function is expanded in terms of the two linearly independent D functions each multiplied by an associated Hylleraas-type radial function with two nonlinear parameters. Calculations have been done employing up to a total of 168 linear parameters, so that convergence can be examined and extrapolations in most cases performed to $N=\infty$. In addition, adiabatic and nonadiabatic corrections have been included. Results are found to be larger than Armstead's in all cases, near the upper edge of his estimated uncertainty. The calculation confirms as a byproduct that there are no $p$ -wave Feshbach resonances in this energy range.

• Received 20 September 1973

DOI:https://doi.org/10.1103/PhysRevA.9.219