High-spin, multiparticle isomers inSb121,123

G. A. Jones, S. J. Williams, P. M. Walker, Zs. Podolyák, S. Zhu, M. P. Carpenter, J. J. Carroll, R. S. Chakrawarthy, P. Chowdhury, I. J. Cullen, G. D. Dracoulis, A. B. Garnsworthy (+8 others)
2008 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
more » ... 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 [404] 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.
doi:10.1103/physrevc.77.034311 fatcat:4zqarlokmbg53amhsajmwvcvsu