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The first gamma ray source to be discovered was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray almost immediately upon formation. [note 1] Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium.
60 Co Decay, with spins and parities shown. Alpha- beta- and gamma rays can only be emitted if the conservation laws (energy, angular momentum, parity) are obeyed. This leads to so-called selection rules. Applications for gamma decay can be found in Multipolarity of gamma radiation. To discuss such a rule in a particular case, it is necessary ...
Likewise, gamma radiation and X-rays were found to be high-energy electromagnetic radiation. The relationship between the types of decays also began to be examined: For example, gamma decay was almost always found to be associated with other types of decay, and occurred at about the same time, or afterwards.
The main advantage of 60 Co is that it is a high-intensity gamma-ray emitter with a relatively long half-life, 5.27 years, compared to other gamma ray sources of similar intensity. The β-decay energy is low and easily shielded; however, the gamma-ray emission lines have energies around 1.3 MeV, and are highly penetrating.
It has a half-life of 30 years, and decays by beta decay without gamma ray emission to a metastable state of barium-137 (137m Ba). Barium-137m has a half-life of a 2.6 minutes and is responsible for all of the gamma ray emission in this decay sequence. The ground state of barium-137 is stable. The photon energy (energy of a single gamma ray) of ...
Types of radioactive decay include gamma ray; beta decay (decay energy is divided between the emitted electron and the neutrino which is emitted at the same time) alpha decay; The decay energy is the mass difference Δm between the parent and the daughter atom and particles. It is equal to the energy of radiation E.
In such cases, de-excitation cannot take place by emission of a gamma ray, since this would violate conservation of angular momentum, hence other mechanisms like IC predominate. This also shows that internal conversion (contrary to its name) is not a two-step process where a gamma ray would be first emitted and then converted.
Potassium-40 undergoes four different types of radioactive decay, including all three main types of beta decay: electron emission (β −) to 40 Ca with a decay energy of 1.31 MeV at 89.6% probability, positron emission (β + to 40 Ar at 0.001% probability, [1] electron capture (EC) to 40 Ar * followed by a gamma decay emitting a photon [Note 1 ...