Magnetic Rotation in the A = 80 Region: M1 Bands in Heavy Rb Isotopes.

ABSTRACT

We have studied the isotopes (82)Rb45, (83)Rb46, and (84)Rb47 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 (11)B + (76)Ge 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 (82)Rb and (84)Rb 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 [Formula see text]. This is the first evidence of magnetic rotation in the A ≈ 80 region. In contrast, the M1 sequences in the odd-even nucleus (83)Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.