The strong-interaction fine and hyperfine structure of antiprotonic atoms

Abstract

The spin-dependent structure of the energy levels of antiprotonic atoms is investigated by microscopic calculations based on phenomenological two-body nucleon-antinucleon interactions. The quadratic spin-orbit part of the two-body interaction is expected to be small and is neglected, but all the other terms are included. Energy shifts and widths are calculated using harmonicoscillator wave functions for light nuclei below Ca, and the droplet-model nuclear-density distributions for heavier nuclei. The fine and hyperfine structure are obtained as a function of proton number. They are comparable in size and very complicated but are mainly due to the two-body spin-spin and spin-orbit interactions. The spin-structure effects are conceivably largest for odd nuclei with high ground-state angular momenta. The agreement with the available data is in general very good, being in most cases within the experimental uncertainty.