Beta electrons and conversion electrons
The example chosen is that of caesium-137, well known a beta-rays emitter. In 85.1% of cases the beta electron is accompanied in 85.1% of cases by a 661.57 keV gamma ray and in 9.6% of cases by an electron conversion. While the energy distribution of beta electrons is continuous, the conversion electrons have a unique energy depending on the atomic layer from which they originate. The most common conversions occur in layer K. In the case of caesium-137, conversion electrons carries on average 5% of the decay energy.