Eur. Phys. J. A 2, 325–326 (1998) T HE EUROPEAN P HYSICAL JOURNAL A c  Springer-Verlag 1998 Short note Band structures in doubly-odd 100 Rh A. Gizon 1 , Gh. C˘ ata-Danil 1, a , J. Gizon 1 ,J.Tim´ar 2 , B.M. Nyak´ o 2 , L. Zolnai 2 , A.J. Boston 3 , D.T. Joss 3 , E.S. Paul 3 , A.T. Semple 3 , N.J. O’Brien 4 , C.M. Parry 4 1 Institut des Sciences Nucl´ eaires, IN2P3-CNRS/Universit´ e Joseph Fourier, F-38026, Grenoble Cedex, France 2 Institute of Nuclear Research, H-4001 Debrecen, Hungary 3 Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom 4 Department of Physics, University of York, Heslington, York, Y01 5DD, United Kingdom Received: 27 April 1998 Communicated by B. Herskind Abstract. High spin states of 100 Rh have been populated using the reaction 70 Zn+ 36 S at 130 MeV. γ-rays were detected with the EUROGAM2 array. The level structure of 100 Rh has been extended up to 14.41 MeV excitation energy. Several band structures are observed. A band based on a I π =8 - state is developed up to the I π =24 - level. It is assigned as the πg -5 9/2 νh 11/2 configuration. PACS. 23.20.Lv Gamma transitions and level energies – 27.60.+j 90 ≤ A ≤149 Transitional nuclei with Z<50 and A≃100 are character- ized by a very γ -soft potential and a small quadrupole deformation at low and moderate angular momenta. The doubly-odd nuclei have configurations which are domi- nated by the odd proton in orbitals (g 9/2 , p 1/2 , f 5/2 ) sit- uated below the Z=50 gap and the odd neutron in or- bitals (d 5/2 , g 7/2 , h 11/2 ) situated above the N=50 gap. This induces complex level structures for which the pro- ton and the neutron occupy high-Ω and/or low-Ω orbitals. In addition, the coexistence of spherical and deformed shapes increases the complexity of the level structures. In this article high-spin data obtained for the doubly-odd (Z=45,N=55) nucleus 100 Rh are presented together with proposed configurations of observed band structures. The reaction 70 Zn( 36 S,p5n) at a bombarding energy of 130 MeV has been used to populate states in 100 Rh. The beam was provided by the Vivitron accelerator, Stras- bourg. The target was made of two stacked self-supporting foils of Zn, enriched to 70% in 70 Zn, each with a thick- ness of 440 μg·cm -2 . The γ -rays were detected by using the EUROGAM Phase2 array [1]. Coincidence events were collected when at least four suppressed Ge detec- tors fired. A total of 6×10 8 Compton-suppressed events were written on magnetic tapes. After unpacking off-line the higher fold events, a non-gated and several gated E γ1 − E γ2 − E γ3 cubes have been produced and analysed using the LEVIT8R graphical spectrum analysis package a Permanent address: HHIPNE, R-76900, Bucharest, Roma- nia [2]. R DCO ratios and the linear polarisation of γ -rays have been measured. Low-energy levels established by the 99 Ru+α [3] and 96 Mo+ 7 Li [3] [4] fusion-evaporation reactions were used as a starting basis for our level scheme (Fig. 1). In our ex- periment the reaction induced by 36 S ions favours strongly the population of yrast and yrare states. This explains why the positive-parity states based on the I π =5 + ,(T 1/2 =4.6 min) and I π =7 + ,(T 1/2 =140 ns) isomers are weakly fed and no new positive-parity level identified. The positive- parity states are not represented in the partial level scheme of Fig. 1. The I π =8 - state at an excitation energy of 1.163 MeV above the 4.6 min isomer [4] is the basis of a complex ensemble of states extending up to 14.41 MeV excitation. This ensemble is constituted of several band structures, two of them being discussed in the present pa- per: Band 1: This band develops from I π =8 - up to I π =24 - and 21 - for the α=0 and α=1 signature branches, respec- tively. It is strongly populated. The spacings between the lowest levels are very close to those observed in the iso- tope 102 Rh [5] [6] and neighbouring doubly-odd nuclei (e.g. 102 Ag [7] [8]). The intensities of the stretched E2 transitions do not follow a pattern typical of a collective band. The I π =15 - level deexcites to both the I π =14 - level in band 1 and the I π =14 - level in band 2 by two intense M1 transitions (368 and 459 keV) while the 885 keV, E2 transition is extremely weak (one order of magnitude smaller than the other E2 transitions in the same signature cascade). The