It is shown that the 4.1-hr. period of indium can be produced by nuclear excitation of indium and is to be attributed to an excited metastable state, of the stable . This result is obtained by studying the radioactivity produced in indium by neutrons of different energy distributions and by studying the chain reactions produced in cadmium by fast neutrons. It is found that can be produced from by 2.5-Mev neutrons, but not noticeably by strong sources of photoneutrons which have energies of a few hundred thousand electron volts. A radioactive of 2.5-day half-life time is found to transform with emission of negative electrons into . was produced by neutron loss from and by neutron capture from .
- Received 5 November 1938
- Published in the issue dated January 1939
© 1939 The American Physical Society