Shell-model States and Collectivity in⁸³Br₄₈ and ⁸⁵Rb₄₈

Excited states of the nuclei ⁸³Br and ⁸⁵Rb were populated
in the reaction ⁸²Se(⁷Li,alpha2n) and ⁸²Se(⁷Li,4n),
respectively, using the ⁷Li beams of the FN tandem accelerator
in Cologne (E=32 MeV) and of the 120 cm cyclotron in Rossendorf (E=35 MeV).Gamma-gamma-particle
coincidences were measured with six Ge and fourteen Si detectors installed
at the detector array Cologne OSIRIS CUBE. This technique enabled a reaction
channel selection. Multipole orders of the gamma-rays were derived from
directional correlations of coincident gamma-rays and from angular distributions.
Mean lifetimes were deduced for seven levels in ⁸³Br and two
levels in ⁸⁵Rb using the Doppler-shift-attenuation method. The
level scheme of ⁸³Br has been extended up to (21⁺/2)
and 15^-/2 states. In ⁸⁵Rb a level sequence built
on the ground state has been established up to 15^(-)/2 and a
new cascade of fast M1 transitions 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 inboth nuclei have been interpreted
in terms of the shell model. The calculations performed in the model space
pi(0g_9/2, 1p_1/2, 1p_3/2, 0f_5/2)
v(0g_9/2, 1p_1/2) reproduce single-particle characteristics
as well as collective properties of the level sequences.