Cobalt 60 gamma spectrum:
The excited states of nickel 60 are reached when cobalt 60, an isotope widely used in medicine, undergoes beta decay. On the nucleus’s path to the ground state, it emits a number of gamma rays to expend the extra energy it possesses. The diagram above shows the energy and the frequency of these gamma. It shows also that two of these gamma rays are emitted virtually 100% of the time. These two gamma rays emitted in cascade have an energy of around 1 MeV. The presence of these two characteristic gamma ray energies (1.17324 and 1.33250 MeV) serves as an extraordinarily sensitive indicator of the cobalt 60 decay.