Magnetic dipole bands in 82Rb, 83Rb and 84Rb

We have studied the isotopes 82Rb45, 83Rb46 and 84Rb47 to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A=80. Excited states in these nuclei were populated via the reaction 11B+76Ge with E=50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a γ-coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei 82Rb and 84Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13−⩽Jπ⩽16−. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp)πg9/22νg9/2. This is the first evidence of magnetic rotation in the A≈80 region. In contrast, the M1 sequences in the odd-even nucleus 83Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.