High-resolution studies of the gamma rays from isomeric states with half-lives of 10 μs - 30ms in nuclei with Z = 63−83

Abstract

Eight new isomeric states with half-lives in the range 10 μs-30 ms have been identified following bombardment with 17.5 MeV protons of the natural elements and separated isotopes of the elements Eu to Pb. Improved data on 14, previously reported, isomeric states have also been obtained. The energies, half-lives and multipolarities of the gamma rays from these states have been measured using an 8 cm 3 Ge(Li) detector. In most cases, level schemes have been constructed, and the spin and parity of the isomeric level and intermediate levels populated in the decay have been determined. A group of hindered E2 transitions have been observed, all of which are retarded by approximately the same degree e.g. 3 × 10 −3 Weisskopf units. The results are discussed in terms of the Nilsson model and in terms of the selection rules for transitions between Nilsson states.