Example of the Iodine-131 decays
The energy available in the decay is important, 970,8 keV. Eight energy levels of the son-nucleus (xenon 131) are accessible. The three most frequent ways are represented by the red arrows. 89.6% of beta decays lead to the 364 keV energy. The excited nucleus then emits either a 364 keV gamma gamma or two consecutive 284 and 80 keV ones. Other levels joined the ground state, either directly or by cascading to the ground state emitting one or more gamma rays. Only those with a frequency above 1% have been represented on the diagram.