Indium, silver, rhodium, manganese and dysprosium have been rendered radioactive by exposure to slow neutrons from a 200 millicurie radon-beryllium source surrounded by paraffin, and their beta-ray spectra obtained by the cloud-chamber method. The plots of the energy distributions were transformed into straight lines according to the Konopinski-Uhlenbeck formula, and extrapolated to find the upper energy limits. The fit with the K-U theory was found to be good. The extrapolated upper energy limits found were: In (54-minute period), 1.3 MEV; In (13-second period), 3.2 MEV; Ag, 2.8 MEV; Rh, 2.8 MEV; Mn, 2.8 MEV; Dy, 1.4 MEV.

• Received 3 April 1936

DOI:https://doi.org/10.1103/PhysRev.49.793