Beta particle emission energy

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. 

The decay scheme of the naturally occurring radionuclide (see Fig. 9.6) is 89.1% by beta-particle emission, 10.9% by electron capture, and 0.001% by positron decay. The 1311-keV maximum-energy beta-particle decay is to the ground state of " °Ca. Electron-capture decay is followed instantaneously by emission of a 1461-keV gamma ray from the excited state of °Ar to its ground state. Electron capture decay to the ground state is 0.2% per disintegration. 

Occupational exposure due to radioiodine occurs in the nuclear industry, in nuclear medicine and in research. One common exposure is due to a short lived radioisotope (half-life 8 d) which decays with the emission of both beta particles (average energy for main emission 0.19 MeV) and gamma radiation (main emission 0.36 MeV) [43], Iodine is rapidly absorbed into the circulation following inhalation or ingestion, is concentrated in the thyroid, and is excreted predominantly in urine [34, 36]. Thus, after an intake, may be detected directly by measurement of activity in the thyroid, or indirectly in urine samples. 

Emission of an alpha or beta particle often produces an isotope in an unstable, high-energy state. This excess energy is released as a gamma ray, y, or an X-ray. Gamma ray and X-ray emission may also occur without the release of alpha or beta particles. 

Gamma ray The shortest wavelength and highest energy type of all electromagnetic radiation. It originates in the nucleus of radioactive isotopes along with alpha particle, beta particle, or neutron emissions. 

Several different mechanisms, most importtuitly alplia particle, beta particle, and gamma ray emissions accomplish radioactive transformations. Each of these mechanisms is a spontaneous nuclear transformation. Tlie result of tliese transformations is the formation of different stable elements. Tlie kind of transformation that will ttike place for any given radioactive element is a function of the type of nuclear inslabilitv as well as the mass/energy relationship. The nuclear instability is dependent on the ratio of neutrons to... 

Man-made radioactive atoms are produced either as a by-product of fission of uranium atoms in a nuclear reactor or by bombarding stable atoms with particles, such as neutrons, directed at the stable atoms with high velocity. These artificially produced radioactive elements usually decay by emission of particles, such as positive or negative beta particles and one or more high energy photons (gamma rays). Unstable (radioactive) atoms of any element can be produced. 

Tc-99, which has a half life of 2.12 x 10 years, can be recovered from nuclear fission waste in kilogram quantities. Solvent extraction, ion exchange, and volatilization processes are employed to separate it from the numerous other fission products. Because of its long half life and its emission of a soft (low energy) beta particle, it can be safely handled in milligram quantities. Almost all chemical studies of the element have been carried out with this isotope. 

Calculate the maximum kinetic energy of the beta particle emitted in the radioactive decay of 6He. Assume that the beta particle has maximum energy when no other emission is involved. 

An atomic battery for pocket watches has been developed which uses the beta particles from 147Pm as the primary energy source. The half-life of147Pm is 2.62 years. How long would it take for the rate of beta emission in the battery to be reduced to 10% of its initial value ... 

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