High-spin, multiparticle isomers in 121,123Sb

Isomers in near-spherical Z=51, antimony isotopes are reported here for the first time using fusion-fission reactions between 27Al and a pulsed 178Hf beam of energy, 1150 MeV. γ rays were observed from the decay of isomeric states with half-lives, T1/2=200(30) and 52(3)μs, and angular momenta I=((25/2)) and Iπ=(23/2)+, in 121,123Sb, respectively. These states are proposed to correspond to ν(h(11/2))2 configurations, coupled to an odd d(5/2) or g(7/2) proton. Nanosecond isomers were also identified at Iπ=(19/2)- [T1/2=8.5(5) ns] in 121Sb and Iπ=((15/2)-) [T1/2=37(4) ns] in 123Sb. Information on spins and parities of states in these nuclei was obtained using a combination of angular correlation and intensity-balance measurements. The configurations of states in these nuclei are discussed using a combination of spin/energy systematics and shell-model calculations for neighboring tin isotones and antimony isotopes