The problems of resonances in proton-hydrogen and positron-hydrogen scattering are studied. For proton-hydrogen scattering, resonances are predicted at energies just below each of the excitation thresholds. Infinite sequences of resonances are found just as in the electron-scattering case, but the widths are much narrower and these resonances are not presently observable. The positron-hydrogen scattering problem exhibits infinite sequences of resonances just below excitation thresholds, similar to the electron scattering problem. Infinite sequences are also exhibited just below the thresholds for forming excited positronium.

• Received 8 July 1966

DOI:https://doi.org/10.1103/PhysRev.152.76