Internal conversion
In internal conversion (often referred to as IC), the excited nucleus interacts electromagnetically with an orbital electron of the atom. This knocks the electron out of its orbit, leaving an empty space. For this reason, internal conversion electrons are called electron and not beta particle.
History
In the early 1920s, the Austrian physicist Elise Meitner (1878 - 1968) and the English physicist Charles Drummond Ellis (1895 - 1980) were among the first to observe electrons with sharply defined energies during measurements on beta decay. They linked these to gamma-ray transitions in the atomic nucleus, but mistakenly thought that this was a two-step process, in which gamma decay first occurs in the nucleus and then, via a kind of internal photoelectric effect, an orbital electron is released from the atom.
It has, therefore, sometimes been suggested to refer to Meitner-Ellis electrons rather than conversion electrons.