High-spin states of the N = 50 nucleus ⁸⁸Sr were studied via the reaction ⁸⁰Se(¹¹B,p2n) at a beam energy of 45 MeV with the six-detector array OSIRIS CUBE at the University of Cologne. The level scheme of ⁸⁸Sr deduced from this experiment is shown in Fig. 1. On the basis of the analysis of directional correlations of coincident g rays emitted from oriented states (DCO), spin assignments for all observed states were made. Mean lifetimes of three levels were determined using the Doppler-shift-attenuation method. They correspond to strong M1 transitions with B(M1) values of about 0.3 to 1.4 W.u. Shell-model calculations in the model space (0f_5/2, 1p_3/2, 1p_1/2, 0g_9/2) for the protons and (1p_1/2, 0g_9/2, 1d_5/2) for the neutrons were performed. Experimental and calculated level energies of states in ⁸⁸Sr are compared in Fig. 2. Neutron-core excitations are predicted for the lowest 6⁺ and 7⁺ states in agreement with results of previous (d,p) experiments (e.g. [1]). Proton configurations of seniority u = 4 are predicted for the positive-parity states with J^p = 8⁺, 10⁺, 11⁺ and 12⁺. The calculations describe experimental high-spin level sequences with J^p > 7^- and J^p ³ 12⁺ linked by strong M1 transitions as u = 4 and 6 multiplets, respectively, which include proton excitations coupled to neutron-core excitations. A detailed description of this work is given in Ref. [2].

Fig. 1 Level scheme of ⁸⁸Sr deduced from the present experiment.

Fig. 2 Comparison of experimental with calculated level energies in ⁸⁸Sr.

¹ FZR and Institute for Nuclear Research and Nuclear Energy, BAS, 1784 Sofia, Bulgaria
² Institut für Kernphysik, Universität zu Köln, 50937 Köln, Germany

References

[1] P.C. Li et al., Nucl. Phys. A 462 (1987) 26
[2] E.A. Stefanova et al., Phys. Rev. C 62 (2000) 054314  IKH 06/22/01 © E. A. Stefanova