Search results
Results From The WOW.Com Content Network
Electron capture happens most often in the heavier neutron-deficient elements where the mass change is smallest and positron emission is not always possible. When the loss of mass in a nuclear reaction is greater than zero but less than 2m e c 2 the process cannot occur by positron emission, but occurs spontaneously for electron capture.
Nuclei which decay by positron emission may also decay by electron capture. For low-energy decays, electron capture is energetically favored by 2m e c 2 = 1.022 MeV, since the final state has an electron removed rather than a positron added. As the energy of the decay goes up, so does the branching fraction of positron emission.
Such atoms also typically exhibit Auger electron emission. Electron capture, like beta decay, also typically results in excited atomic nuclei, which may then relax to a state of lowest nuclear energy by any of the methods permitted by spin constraints, including gamma decay and internal conversion decay.
decay (positron emission) of a nucleus is allowed energetically, so too is electron capture allowed. This is a process during which a nucleus captures one of its atomic electrons, resulting in the emission of a neutrino: A Z X + e − → A Z−1 X′ + ν e. An example of electron capture is one of the decay modes of krypton-81 into bromine-81 ...
If the mass difference between the mother and daughter atoms is more than two masses of an electron (1.022 MeV), the energy released in the process is enough to allow another mode of decay, called electron capture with positron emission. It occurs along with double electron capture, their branching ratio depending on nuclear properties.
In about 89.28% of events, it decays to calcium-40 (40 Ca) with emission of a beta particle (β −, an electron) with a maximum energy of 1.31 MeV and an antineutrino. In about 10.72% of events, it decays to argon-40 (40 Ar) by electron capture (EC), with the emission of a neutrino and then a 1.460 MeV gamma ray.
This corresponds to β − decay or electron emission, the only form of beta decay which had been observed when Fajans and Soddy proposed their law in 1913. Later, in the 1930s, other forms of beta decay known as β + decay ( positron emission ) and electron capture were discovered, in which the atomic number becomes less by 1 than that of the ...
The naturally occurring 40 K, with a half-life of 1.248 × 10 9 years, decays to stable 40 Ar by electron capture (10.72%) and by positron emission (0.001%), and also transforms to stable 40 Ca via beta decay (89.28%). These properties and ratios are used to determine the age of rocks through potassium–argon dating. [4]