High-spin, multiparticle isomers inSb121,123
Physical Review C
Isomers in near-spherical Z=51, antimony isotopes are reported here for the first time using fusion-fission reactions between 27 Al and a pulsed 178 Hf beam of energy 1150 MeV. Gamma rays were observed from the decay of isomeric states with half-lives, T 1/2 = 200(30) and 52(3) µs, and angular momenta I= ( 25 2 ) and I π = 23 2 + , in 121,123 Sb, 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
... second isomers were also identified at I π = 19 2 − (T 1/2 = 8.5(5) ns) in 121 Sb and I π =( 15 2 − ) (T 1/2 = 37(4) ns) in 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. PACS numbers: 23.20.Lv, 23.20.En, 25.70.Jj, 27.60.+j * Corresponding author: G.Jones@Surrey.ac.uk 113 ≤A≤121 [5-8]. As the neutron number increases and the closed N=82 shell is approached, however, the excitation energy of these deformed states increases, and the rotational bands are no longer yrast; the π 9 2  state becomes non-yrast in 123 Sb (N=72), increasing in energy to E x =1337 keV [9, 10] . This simplifies the picture dramatically, since all states can be interpreted as spherical single or multi-particle excitations. In particular, many states can be described in terms of those observed in tin nuclei, coupled to an extra proton [11, 12] . Nevertheless, the many valance particles make it difficult to perform detailed shell-model calculations, and comprehensive experimental data provide a benchmark against which to test the development of appropriate theoretical descriptions. This report describes the identification of states in 121,123 Sb from the decay of previously unreported isomeric states.