Ge(Li)–Ge(Li) gamma-ray coincidence studies of the decay of 18.6 h ¹⁵⁹Gd

Abstract

The gamma-ray spectrum of 159 Tb following the β decay of 18.6 h 159 Gd has been studied with high resolution Ge(Li) detectors. Eighteen transitions were observed, two of which are reported here for the first time. The previously reported complex nature of the 617 keV transition has been examined and high resolution studies have revealed a doublet structure with energies 616.5 ± 0.3 and 617.7 ± 0.2 keV and intensities of (2.3 ± 0.6) × 10 −3 % and (15.0 ± 2.3) × 10 −3 % per disintegration respectively. Gamma–gamma coincidence experiments were performed with large volume coaxial and thin window planar Ge(Li) detectors, using the related address technique and on-line computers. These experiments have established levels at 58, 138, 348, 363, 581, 618, 674, and 855 keV. All of the transitions observed in the direct spectrum have been fitted into the level scheme.