抄録
The decay of the isomeric state of yttrium 87 has been reinvestigated by using scintillation and Ge(Li) spectrometers. This work leads to the conclusion for its half life to be 12.5 hours instead of 14 hours obtained in the previous study. A weak branching of a beta ray with a maximum energy of 1.54 MeV was found. It was assigned to be a direct transition from the isomeric state (1g9⁄2) of yttrium 87 to the ground state (1g9⁄2) of strontium 87. This allowed transition was found to be comparatively hindered and its logft value obtained was 7.6. Its branching ratio was found to be (6.2±1.2)×10−3. An end-point energy of a beta ray from the ground state of yttrium 87 was found to be 0.78 MeV. Its logft value was 6.2. The 1.54 MeV beta branching was discussed qualitatively in terms of the pairing theory.
