Observation of a γ-decaying millisecond isomeric state in 128Cd80.

A new high-spin isomer in the neutron-rich nucleus 128 Cd was populated in the projectile fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T 1 / 2 = 6.3 ( 8 ) ms was measured for the new state which was tentatively assigned a spin/parity of ( 15 − ). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129 Cd. In the present experiment no evidence was found for the decay of a 18 + E 6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0 h 11 / 2 and the 0 g 9 / 2 orbit, respectively, which is predicted to exist by the shell model. [ABSTRACT FROM AUTHOR]