Search For Isomeric Transitions In Fission Products Around Mass Number 150

A beta-gated gamma-ray and internal conversion electron measurement system for identifying isomers has been installed to the isotope separator on-line at the Kyoto University Research Reactor. On-line measurements for mass number A = 93 nuclides clearly showed that it had sufficient ability to distinguish isomeric transitions from those following beta-decay. Using this equipment, an isomeric state in Pr-148 was successfully observed at 76.8 keV, and one in Pr-151 at 35.1 keV. We also found a candidate of an isomeric transition in an A = 150 nuclide produced by the thermal neutron-induced fission of U-235.