Beta-decay study on high energy excited levels in nuclei far off stability line with energy-sum gamma-ray spectroscopy.

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With a through-hole type HPGe detector and a clover Ge detector, decay schemes including high energy excited states of nuclei far off the b stability line were studied. These detectors have high solid angle and high detection efficiency, then, de-excite.-rays with cascade relation can be detected as a coincidence summing peak. It means the observed sum peaks correspond to energy of the excited states. Those are useful tools for identify high energy levels. In addition, a correction method for coincidence summing in the clover detector were also developed, the.-ray intensities could be determined with the accuracy of 5%, approximately, from 100 keV to 3 MeV.On the other hand,.-rays in the decay of neutron-rich nucleus 147La, which were separated by the on-line mass separator KUR-ISOL from fission products of 235U with thermal neutron, were measured with the detector. The 56 excited levels and 160.-rays in the daughter nucleus 147Ce were newly identified up to 3. 5 MeV.