The search for isomers of 156Pm through the β-decay of 156Nd

The search for isomers of 156Pm has been performed through the β-decay of 156Nd. The sources of the 156Nd were obtained from mass-separated fission products of 235U at the Kyoto University Reactor (KUR). Plastic scintillators, two HPGe detectors, and a Si(Li) detector were used. In the present experiment, more than 30 γ-rays from the β-decay of the 156Nd were newly observed. The 150.8 keV isomeric transition (I.T.) from 156mPm was successfully measured. This transition was assigned to the M3 multipolarity, from the result of the conversion electron measurement. A spin and a parity of 1- were reasonable for the isomeric state based on the M3 multipolarity of the I.T. and the 4- β-decaying state of the 156Pm. (author)