Shape coexistence near the double-midshell nucleus Rh-111

The decay of Ru-111 obtained from fast on-line chemical and mass separation has been investigated by beta-gamma-t and gamma-gamma coincidence techniques. Earlier spin and parity assignments of Rh-111 levels based on extrapolations of level systematics are confirmed. in particular, the K=1/2 intruder band is supported by the hindrance of E2 transitions between deformed and spherical stales and enhancement of intraband E2 transitions. The excitation energies of intruder hand members in Rh isotopes show a minimum at Rh-109(64), with two neutrons less than Rh-111 at the N=66 midshell. This trend, which differs from the one in the higher-Z neighbouring elements Ag and Cd with minima at N=66, follows the evolution of deformation observed in the lower-Z elements Ru and Mo.