SHELL-MODEL STATES AND COLLECTIVITY IN BR-83(48) AND RB-85(48)

Excited states of the nuclei Br-83 and Rb-85 were populated in the rea ctions (82)Set(Li-7,alpha 2n) and Se-82(7Li,4n), respectively, using t he Li-7 beams of the FN tandem accelerator in Cologne (E = 32 MeV) and of the 120cm cyclotron in Rossendorf (E = 35 MeV). Gamma-gamma-partic le coincidences were measured with six Ge and fourteen Si detectors in stalled at the detector array Cologne OSIRIS CUBE. This technique enab led a reaction channel selection. Multipole orders of the gamma rays w ere derived from directional correlations of coincident gamma rays and from angular distributions. Mean lifetimes were deduced for seven lev els in Br-83 and two levels in Rb-85 using the Doppler-shift-attenuati on method. The level scheme of Br-83 has been extended up to (21/2(+)) or 15/2(-) states. In Rb-85 a level sequence built on the ground stat e has been established up to 15/2((-)) and a new cascade of fast M1 tr ansitions starting with a 17/2((-)) state at 3198.2 keV has been found . Furthermore, several medium-spin states have been newly introduced. The level sequences in both nuclei have been interpreted in terms of t he shell model. The calculations performed in the model space pi(Og(9/ 2), 1p(1/2), 1p(3/2), Of(5/2))v(Og(9/2), 1p(1/2)) reproduce single-par ticle characteristics as well as collective properties of the level se quences.