First observation of the pi 0h(11/2)( )circle times nu 0h(9/2) partner orbital configuration in the odd-odd I-138 nucleus

The beta-decay scheme of Te-138 and the level structure of I-138 is reported for the first time. The experiment was performed at the Radioactive Isotope Beam Factory of RIKEN, as one of the EUROBALL-RIKEN Cluster Array campaigns. Secondary radioactive ions, including Te-138 and Sb-138, were produced by the in-flight fission of a U-238 beam with the energy of 345 MeV per nucleon. From the beta decay of Te-138, the level scheme of I-138 was supplemented with new spin and parity assignments, such as the low-lying negative-parity states and a positive-parity 1(+) state. This 1(+) state can be interpreted as being associated with the pi 0h(11/2) circle times nu 0h(9/2) partner orbital configuration populated by the Gamow-Teller transition between a neutron in the 0h(9/2) orbital and a proton in the 0h(11/2) orbital. Details of the structure of I-138 are discussed in terms of the proton-neutron interactions and Gamow-Teller transition strength within the theoretical context of shell-model calculations.