Origin of odd-even staggering in fragment yields: Impact of nuclear pairing and shell structure on the particle-emission threshold energy

Abstract

Strong odd-even staggering (OES) of the yields of fragments, produced by fragmenting $^{78}\mathrm{Kr}$ projectiles, has been measured by employing the combination of an in-flight fragment separator and a storage ring. It is shown that the OES of fragment yields of ${T}_{z}=\ensuremath{-}1/2$ and ${T}_{z}=1/2$ mirror nuclei critically depends on both pairing and shell structure, especially at the closed shells $Z=20$ and 28. A comparison of the relative OES of yields and of particle-emission threshold energies reveals unambiguously that the origin of the OES of fragment yields is mainly determined by the OES of the particle-emission threshold energies, which contain both pairing and shell effects.