SHAPE COEXISTENCE NEAR THE DOUBLE-MIDSHELL NUCLEUS RH-111

The decay of Ru-111 obtained from fast on-line chemical and mass separ ation has been investigated by beta-gamma-t and gamma-gamma coincidenc e techniques. Earlier spin and parity assignments of Rh-111 levels bas ed on extrapolations of level systematics are confirmed. in particular , the K=1/2 intruder band is supported by the hindrance of E2 transiti ons between deformed and spherical stales and enhancement of intraband E2 transitions. The excitation energies of intruder hand members in R h isotopes show a minimum at Rh-109(64), with two neutrons less than R h-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, foll ows the evolution of deformation observed in the lower-Z elements Ru a nd Mo.