High-spin structure of the neutron-rich Rh-107,109(45) isotopes: the role of triaxiality

The Rh-107,Rh-109 nuclei have been produced as fission fragments following the fusion reaction Si-28 + Yb-176 at 145 MeV bombarding energy and studied with the Eurogam2 array. In both nuclei three new rotational bands with th e odd proton occupying the pi g(9/2), pi p(1/2) and pi (g(7/2)/d(5/2)) sub- shells have been observed. In Rh-107, two other bands involving strong M1 t ransitions have been identified at excitation energy larger than 2 MeV. The y can be interpreted in terms of three quasiparticle excitations. In additi on new structures consisting of four transitions, built on states located a t low excitation energy (680 keV in Rh-107 and 642 keV in Rh-109), point ou t the importance of triaxial deformation in these two isotopes.