Neutron-Induced Radioactivity of Long Life in Cobalt

When cobalt is bombarded by neutrons, an activity of long half-life is obtained. The radioactive element has been shown by a chemical analysis to be an isotope of cobalt. The radiations emitted in the disintegration of this element have been investigated, principally by the absorption method. A gamma-ray is observed with a mass absorption coefficient in Pb of about 0.047 cm²/g, and a spectrum of soft beta-rays with an estimated limiting range of 30 mg/cm² of aluminum, representing an energy of 160 kv. A group of more penetrating particles completely absorbed only by about 0.65 g/cm² of aluminum is also indicated. This group may represent a relatively infrequent disintegration process, in which the total energy is carried off by the beta-particle and no gamma-ray is emitted. Results of a measurement on the half-life indicate that it is 2.0±{}0.5 years.