The structure of the ⁷³Br isotope was investigated by using the EUROBALL spectrometer and the level scheme was published in [1].
To interpret the data, the configuration-dependent Cranked Nilsson-Strutinsky (CNS) approach was applied [2]. The calculations minimize the total energy of a specific configuration for a given spin with respect to the deformation parameters (e₂,e₄,g). The configurations are specified with respect to a ⁵⁶₂₈Ni₂₈ core as having 7 active protons and 10 active neutrons. They are labelled by the shorthand notation [p₁p₂,n₁n₂], where p₁(n₁) stands for the number of protons (neutrons) in the (p_3/2,f_5/2) orbitals and p₂(n₂) stands for the number of protons (neutrons) in g_9/2 orbitals.

In addition, the sign of the signature of the last occupied orbital is given as a subscript, if the number of occupied orbitals in the specific group is odd. The calculated energies of the energetically lowest configurations are compared with experimental energies in Fig. 1, where a rigid rotor reference was subtracted. Based on this comparison the configurations [43₊,64] and [5₊2,64] were assigned to bands A and C, respectively. Band B is observed up to I = (63/2). The calculations suggest that the [5_-2,64] configuration can be assigned to this band at low and medium spin. It is the signature partner of the [5₊2,64] configuration assigned to band C. The [5_-2,64] configuration is crossed at spin 57/2 by the [43₊,7₊3₊] configuration. The predicted crossing is indeed observed in band B at spin (55/2^-). The latter configuration can be related to band B above the band crossing. In the calculations, the [43₊,7₊3₊] configuration (empty triangles in Fig. 1) undergoes a shape change from a collective shape (triaxiality parameter g » +30^°) to a non-collective oblate shape (g = +60^°) between spins 55/2 and 63/2. This means that collective rotation is no longer possible and the corresponding band terminates at spin 63/2. Since this is the highest spin observed for band B, we conclude that we observed band B up to its termination.

¹ FZR and Horia Hulubei NIPNE, Bucharest, P.O. Box MG-6, Romania
² Department of Mathematical Physics, Lund Institute of Technology, P.O. Box 118, 22100 Lund, Sweden
³ Physik-Department der Technischen Universität München, 85747 Garching
⁴ >Laboratory of Radiation Physics, Institute of Solid State Physics, University of Latvia, LV 2169 Salaspils, Latvia
⁵ INFN, Laboratori Nazionali di Legnaro, 35020 Legnaro, Italy>
⁶ Institut für Kernphysik, Universität zu Köln, 50937 Köln
⁷ II. Physikalisches Institut, Universität Göttingen, 37073 Göttingen
⁸ University of York, Physics Department, Heslington, York Y01 5DD, United Kingdom

References

[1]C. Plettner et al., Phys. Rev. C 62, 014313 (2000)

[2]I. Ragnarsson et al., Phys. Rev. Lett. 74, 3935 (1995)  IKH 06/22/01 © C. Plettner