From Big Medical Encyclopedia

ELECTRON CAPTURE — the type of radioactive transformation, at Krom an atomic nucleus takes an electron from electronic a cover therefore one of protons of a kernel turns into a neutron with allocation of a neutrino. Nuclear charge of atom (see an atomic nucleus) after E. h. decreases by unit, and mass number does not change. AA. h. it is caused by surplus of protons in the corresponding radionuclide (see Isotopes). Many radionuclides used in medicine for radiation therapy (see), radio isotope diagnosis (see) and with the research purposes possess E. h.

At E. h. capture of an electron from the next to an atomic nucleus (see) energy level is most probable (so-called. K-capture); capture of an electron from the following level (L-level) by about 100 times is less probable, than K-capture.

Unlike electronic and positron disintegrations (see the Beta decay) the neutrinoes which are formed at E. h., have identical energy (monoenergetic neutrinoes). AA. h. is the characteristic of radionuclide, but not a chemical element (see. Chemical elements), and at various isotopes occurs differently. The kernels possessing E. h., are characterized by a so-called exit to disintegration, relative size (as a percentage), testimonial of quantity of the breaking-up atomic nuclei possessing E. h. E.g., at 40/10K the exit to disintegration is equal to 11% (see Potassium) while 89% of other atomic nuclei of this element are exposed to a usual beta decay. After absorption of an electron at E. h. the vacant place is taken by an electron from more high energy level. At the same time atom emits characteristic x-ray emission (see), on Krom it is possible to establish existence E. h. and to define amount of radioactive material.

Bibliography: Gusev N. G. and Dmitriyev P. P. Quantum radiation of radioactive nuclides, M., 1977; Parker R., Smith P. and Taylor D. Bases of a nuclear medicine, the lane with English, M., 1981.

R. V. Stavitsky.