Magnetic rotation in the A = 80 region: M1 bands in heavy Rb isotopes

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 -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^-≤J^π≤16^-. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp) πg_9/2 ² vg_9/2. 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.