Internal conversion - Naibutenkan

This is the process in which an atomic nucleus transfers its excitation energy to an extranuclear electron and releases an electron. The energy of the electron is equal to the difference between the excitation energy and the binding energy between the electron and the nucleus, and is a single energy, unlike electrons in beta decay. There is no change in the structure of the nucleus, and only an electron from an extranuclear orbit is ejected, so in this respect it also differs from beta decay. An electron from an outer orbit falls into the vacant orbit, and the energy released is released as a characteristic X-ray or sometimes ejects one of the other orbital electrons. The ratio of the number of internal conversion electrons to the number of gamma photons emitted from a certain radioisotope is called the internal conversion coefficient, and is symbolized by α. However, since the process in which an excited nucleus loses its energy is more likely to occur by emitting gamma rays, α is usually less than 1.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

原子核がその励起エネルギーを核外電子に与えて電子を放出する過程をいう．このとき，電子のもつエネルギーは，励起エネルギーと電子-原子核間の結合エネルギーとの差に等しく，β崩壊にもとづく電子の場合と異なり，単一エネルギーである．また，原子核の構成にはなんの変化も起こらず，核外の軌道電子が飛び出すだけであるから，この点でもβ崩壊とは異なる．なお，空になった軌道には，さらに外側の軌道から電子が落ち込み，このとき遊離されるエネルギーが特性X線として放出されるか，ときにはほかの軌道電子の一つを飛び出させる．ある放射性同位体から放出されるγ光子数に対する内部転換電子数の比を内部転換係数といい，記号としてαを用いるが，励起核がそのエネルギーを失う過程は，γ線を放出して行われる確率のほうが大きいので，αは通常1以下である．

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