Positron-hydrogen resonances associated with theN=2positronium andN=3hydrogen thresholds

Some lower-lying S-wave resonances in positron-hydrogen scattering associated with the positronium N=2 and hydrogen N=3 thresholds are investigated using the method of complex-coordinate rotation and using an adiabatic treatment in hyperspherical coordinates. Both calculations indicate that the lowest resonance associated with the positronium N=2 threshold lies near E=-0.150279 Ry, in disagreement with Doolen's prediction that the lowest resonance occurs at E=-0.222 Ry. We also report for the first time resonance parameters associated with the hydrogen N=3 threshold.