Z. Phys. A - Atomic Nuclei 325, 27-35 (1986) Zeitschrift for Physik A Atomic Nuclei 9 Springer-Verlag1986 Level Structure of Proton-Rich N=83 Nuclei S~ and lSZTm* J. McNeill, R. Broda ~, Y.H. Chung 2, P.J. Daly, Z.W. Grabowski, H. Helppi 3, and M. Kortelahti 4 Purdue University, W. Lafayette, Indiana, USA R.V.F. Janssens, T.L. Khoo, R.D. Lawson, and D.C. Radford 5 Argonne National Laboratory, Argonne, Illinois, USA J. Blomqvist Research Institute for Physics, Stockholm, Sweden Received May 20, 1986 The yrast levels of the N=83 odd-odd nuclei ~S~ and 152Tm have been studied by 7-ray spectroscopy following reactions induced by 240-250 MeV 6~ ions. Isomers have been identified in tS~ at 1.096, 2.625 and ~8.0 MeV and in aSZTm at 2.555 and ~6.3 MeV, and the level schemes of both nuclei have been established up to 2.6 MeV. The level spectra are interpreted using the shell model in terms of the coupling of anfT/2, h9/z or i~3/2 valence neutron to the yrast excitations of the neighboring N= 82 nuclei. PACS: 21.60.Cs; 23.20.Ck; 23.20.Lv I. Introduction The N=83 species lS~ and 152Tm are odd-odd nuclei having three and five valence protons outside the 146Gd core and a single valence neutron. Studies of these nuclei should provide information about the proton-neutron residual interaction. Further, it is of interest to investigate how the structural trends and variations of transition probabilities observed [1-3] in the N= 82 series of isotones are affected by the additional valence neutron. The high-j neutron orbit- als above N=82 are f7/2, h9/2 and i~3/2. The yrast spectra of ~5~ and ~52Tm are thus expected to arise from the coupling of the yrast excitations of the N= 82 nuclei 149Ho and 151Tm with the valence * Work supported by the U.S. Department of Energy 1 Permanent address: Institute of Nuclear Physics, PL-30055 Cra- cow, Poland 2 Present address: Hallym University, Choon-Cheon, Korea 3 Permanent address: Lapeenranta University of Technology,SF- 53851 Lapeenranta, Finland 4 Permanentaddress: Universityof Jyvfiskyl~, SF-40100Jyv/iskylfi, Finland s Present address: Chalk River Nuclear Laboratories, Ontario, Canada KOJ iJO neutron, and since the vfT/2 lies 1 MeV or more below the vh9/e and vi13/2 states, excitations of the type (7~hll/2)nvfT/2 should be particularly prominent. The nuclei lS~ and ~52Tm each have two low-lying t% decaying isomers [4, 5]. The higher spin isomer in each case is believed to be mainly the two-quasiparti- cle configuration (ZChl~/Z vfT/z)9 +, which decays by a fast allowed Gamow-Teller r162 transition to a (vh9/2 vf7/2)8 + state in the N= 84 daughter nucleus. For convenience, we shall refer to these 9 + isomers as the nuclear ground states. We previously investigated the structure of 1S~ using 12aSb(32S,3n) and 122Te(3ZS,p3n) reactions, and reported [6] a level scheme up to a 92 ns 17 + isomer at 2,625 keV. The main yrast level sequence was found to agree well with shell model predictions for the (7chll/2)3vfT/2 configuration. Other levels identified included an 11- octupole excitation at 1,096 keV, 13- and 15- states with the main configu- rations (~r ht a/2) z 7r sl/2 v f7~2 and (Tr h~ a/z) 2 zcd3/2 v f7~2, and a 12- state of the type (zch~a/2)3 vi~3/2, mainly seniority two (v-- 2). The 17 + ~ 15 + transition in 15~ was found to be approximately twice as fast as the 27/2 --*23/2 transition in a49Ho, demon-