Gamma-Rays and Nuclear Levels Associated with Radioisotopes of Europium, Erbium, and Cerium

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Abstract
The energies of the conversion electrons associated with the decay of 8 radioisotopes were measured using permanent magnet-type photographic beta-spectrometers. The energies of the gamma-rays associated with the various activities are as follows: europium 152 (9.2-hr) 121.9, 344.1 kev; erbium 171 (7.5-hr) 112.8, 117.9, 125.5, 176.4, 294.5, 307.5, 419.7 kev; cerium 137 (36-hr) 253.4 kev; cerium 139 (140-day) 166.0, 275.2 kev; cerium 141 (28-day) 145.7 kev; cerium 143 (33-hr) 57.5, 290.6, 348.4 kev; cerium 144 (300-day) 34.0, 41.3, 46.8, 53.7, 80.9, 95.0, 100.5, 134.5 kev; and praseodymium 144 (17.5-min) 61.0 kev. Energy level schemes are proposed for each product nucleus.