Observation of a rigid-rotational band in the N=Z+1 nucleus ^79Y.^*

Characteristic γ rays in the N=Z+1 nucleus ^79Y were identified using the reaction ^28Si(^54Fe, p2n)^79Y at 200 MeV and a detection system that consisted of the ORNL Clover Array, RMS, and an ionization chamber for Z-selection. Furthermore, Gammasphere data obtained in the reaction ^58Ni(^28Si, α p2n)^79Y at 130 MeV were used to investigate the coincidence relationship between these γ rays, and to establish a strongly-coupled rotational band that is most likely associated with the proton g_9/2 orbital. A striking feature of this band is that its J^(1) and J^(2) moments of inertia are nearly equal and almost constant (≈ 19 MeV/hbar^2), which is indicative of a rigid-body like rotational behavior. These results are in good agreement with self-consistent TRS calculations which predict a large deformation ,β₂ ≈ 0.4. ^* work supported in part by US Department of Energy under contract No. DE-AC05-96OR22464.