Recoil energy, beta particles

In all cases the recoil energy is too low to break the chemical bond (about 2.5 eV for one bond). The probability of interaction of the emitted beta particles directly with the electrons of the atom is also small. The non-adiabatic change (increase or decrease) of the nuclear charge in p - and /J -emissions results in ionization of the peripheral shell electrons, when the probability of ionization of K, L and M shells equals 10 , 10 and 5 X 10 only . 

The neutrino and antineutrino groups carry somewhat more than half of the decay energy, while the beta-particle group carries somewhat less than half. The kinetic energy of the product nuclide is very small because of the several-thousandfold smaller beta-particle mass. This recoil energy, in the range of a few electron volts, nevertheless may cause chemical change such as displacement of an atom from a crystal lattice. 

Positron emission occurs only when the energy difference between the parent radionuclide and the products exceeds 1.02 MeV (the energy equivalent of the sum of the masses of an electron and a positron). The atom s recoil, as for beta-particle emission, is a few electron volts. At lesser energy differences, a proton in the nucleus can be converted to a neutron by electron capture, i.e., the capture by the nucleus of an atomic electron from, most probably, an inner electron shell (see discussion below of CEs). The process of electron capture parallels positron emission and may occur in the same isotope. It is accompanied by emission of a neutrino and characteristic X rays due to the rearrangement of atomic electrons. Electron capture may also be signaled by the subsequent emission of gamma rays. Examples of these decays are given in Sections 9.3.4 and 9.3.6. 

Each radionuclide among the more than one thousand that are known has a unique decay scheme by which it is identified. For this reason, among others, researchers have studied decay schemes over the years and their reported information has been compiled and periodically updated. The compiler surveys the reported information for each radionuclide and attempts to select the most reliable information for constructing a self-consistent decay scheme. The fraction of beta particles that feed an excited state must match the fraction of gamma rays plus conversion electrons emitted by the excited state. The energy difference between any two states must be consistent with the energies of the transition radiations plus the recoil energy of the atom that emitted the radiations. 

Recently, experiments on nuclear decay have started to use MOTs as a source of cold, well-localized atoms. The low-energy recoiling nuclei can escape from the MOT and be detected in coincidence with, 3-decays to reconstruct information about the properties of the particles coming from the nuclear reactions. An example of such an experiment is a beta- neutrino correlation measurement on laser-trapped 38mj ... 

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