BETA-DECAY OF DY-157

The decay of Dy-157(T-1/2 = 8.14(4)h) is investigated. Spectra of gamm a-rays, internal conversion electrons and gamma - gamma coincidences a re 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 Tb-157 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 f or 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 int roduced levels. The structure of the excited states of Tb-157 is discu ssed in terms of current nuclear models.