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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.
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 ...
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.
In electric multipole radiation, the electric field has a radial component; in magnetic multipole radiation, the magnetic field has a radial component. [1] An example: in the simplified decay scheme of 60 Co above, the angular momenta and the parities of the various states are shown (A plus sign means even parity, a minus sign means odd parity ...
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 ...
Barium-137m has a half-life of about 153 seconds, and is responsible for all of the gamma ray emissions in samples of 137 Cs. Barium-137m decays to the ground state by emission of photons having energy 0.6617 MeV. [8] A total of 85.1% of 137 Cs decay generates gamma ray emission in this manner.
Iridium-192 is a very strong gamma ray emitter, with a gamma dose-constant of approximately 1.54 μSv·h −1 ·MBq −1 at 30 cm, and a specific activity of 341 TBq·g −1 (9.22 kCi·g −1). [ 4 ] [ 5 ] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV .
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.