Radiation ofCo55

The radiations of ${\mathrm{Co}}^{55}$ have been studied in a thin lens magnetic beta-ray spectrometer and in coincident scintillation spectrometers. By observation of the internal conversion lines and the unconverted gamma-spectrum, gamma-rays of energies 1410, 937, 476, and 247 kev have been resolved. No other gamma-ray of higher energy decaying with an 18-hr half-life could be observed after careful search of that region using a 4½-in. diam and 4-in. thick NaI(Tl) crystal. The Fermi-Kurie analysis of the positron spectrum yielded three groups of positrons of maximum energies 1510 (51%), 1040 (45%) and 790 (4%) kev. These measurements revealed energy levels of the residual nucleus, ${\mathrm{Fe}}^{55}$, at 937, 1410, and 1657 kev.