High-spin, multiparticle isomers in {sup 121,123}Sb

Isomers in near-spherical Z=51, antimony isotopes are reported here for the first time using fusion-fission reactions between {sup 27}Al and a pulsed {sup 178}Hf beam of energy, 1150 MeV. {gamma} rays were observed from the decay of isomeric states with half-lives, T{sub 1/2}=200(30) and 52(3){mu}s, and angular momenta I=((25/2)) and I{sup {pi}}=(23/2){sup +}, in {sup 121,123}Sb, respectively. These states are proposed to correspond to {nu}(h{sub (11/2)}){sup 2} configurations, coupled to an odd d{sub (5/2)} or g{sub (7/2)} proton. Nanosecond isomers were also identified at I{sup {pi}}=(19/2){sup -} [T{sub 1/2}=8.5(5) ns] in {sup 121}Sb and I{sup {pi}}=((15/2){sup -}) [T{sub 1/2}=37(4) ns] in {sup 123}Sb. 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.