Transition strengths for decays from low-lying states in A ~ 70 nuclei have been deduced from lifetime measurements using the recoil distance Doppler shift technique. The results confirm the collectivity previously reported for the 21+→0gs+ decay in Se and reveal a relative decrease in collectivity in Br. This trend is reproduced by shell model calculations using the GXPF1A interaction in an fp model space including the Coulomb, spin-orbit and isospin non-conserving interactions. The 31+→21+ decay in Br is found to have a very small B(M1) value, which is consistent with the configuration of the state being dominated by the coupling of f52 protons and neutrons. The results suggest that the g92 orbit does not play an important role at low spin in these nuclei. The B(E2) values for the decays of the (T = 1) 21+ states in Br and Se are almost identical, suggesting there is no major shape change between the two nuclei at low spin.
|Number of pages||6|
|Journal||Physics Letters B : Nuclear, Elementary Particle and High-Energy Physics|
|Early online date||15 Apr 2014|
|Publication status||Published - 2 Jun 2014|
- Physics - Professor
- Physics - Emeritus Professor