Beta decay of 157Dy

The decay of ¹⁵⁷Dy(T_1/2 = 8.14(4)h) is investigated. Spectra of γ-rays, internal conversion electrons and γ ? γ coincidences are measured. The 983.50 and 991.70 keV transitions show E0 admixtures. Our experimental results made it possible to extend substantially the decay scheme. From the coincidence relationships we established four new excited states of ¹⁵⁷Tb at 883.32, 895.06, 925.29, 970.38 keV and confirmed the 357.66 keV state. The levels at 1160.71 and 1318.62 keV are introduced from the energy balance. Tentative evidence is given for the existence of five new levels at 252.58, 327.65, 658.36, 793.52 and 922.69 keV. We assign Nilsson’s quantum characteristics to all introduced levels. The structure of the excited states of ¹⁵⁷Tb is discussed in terms of current nuclear models.