Beta-decay half-lives and neutron-emission probabilities of very neutron-rich Y to Tc isotopes

Neutron-rich Y-39 to Tc-43 isotopes have been produced by fission of uranium with a 50 MeV H-2(+) beam, Beta-decay half-lives, delayed neutron-emission probabilities, and production yields have been measured and compared with theory. Beta decay of 4 new isotopes is reported, and the beta-delayed neutron-emission mode has been discovered for 12 isotopes of the elements niobium and technetium. The results compared to quasiparticle random phase approximation predictions indicate the increasing importance of fast beta transitions to high-lying states of nuclei with large neutron excess

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

Shape coexistence near the double-midshell nucleus 111^{\bf 111}Rh

The decay of $^{111}$Ru 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 $^{111}$Rh 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 states and enhancement of intraband E2 transitions. The excitation energies of intruder band members in Rh isotopes show a minimum at $^{109}$Rh$_{64}$, with two neutrons less than $^{111}$Rh 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

Beta-decay studies of nuclei far from stability near N=28

NESTER AC

Triaxiality near the 110Ru ground state from Coulomb excitation

A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2=12 s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations