York

The orbital electron capture indicates a reaction of Nuclear physics during which a Atomic nucleus captures a electron located on an electron shell of the atom. The consequence of the capture, according to the Loi of conservation, is that there is a transmutation of the atom since a Proton, by absorbing the intruding electron becomes a Neutron, and emission of a electronic neutrino to preserve the lepton Nombre; the atom which had p protons and N neutrons becomes an atom with p-1 protons and n+1 neutrons.

$e^-\; +\; p\; \backslash \; rightarrow\; N\; +\; \backslash \; nu\_e$

A theoretical application, that one could consider by looking at the periodic Tableau of the elements, would be to produce gold with mercury or even with lead. However, the quantities of energy concerned to inject electrons in the cores of the lead or mercury atoms are so large, and the probability of obtaining the so weak desired reaction (it brings into play the weak Interaction), that the operation is financially more expensive than remunerative.

In fact, the phenomenon of capture occurs only for Nucléide S close relations of disintegration β ⁺ , but for which the weight breakdown (see the section instability of the particles) is unfavourable. Indeed, to produce a disintegration β ⁺ , i.e. a reaction

$p\; \backslash \; to\; N\; +\; e^+\; +\; \backslash \; nu$

the weight breakdown is négatif : m_n –   m_p   =  1,29   MeV, and m_e  =  0,55   MeV. It is necessary thus that the final core is at least of 1,84   MeV lighter than the initial core so that disintegration can occur, mass of the neutrino being in all the negligible cases. On the other hand, in the case of the orbital electron capture, the mass of the electron results from the difference in mass neutron-proton in the assessment of the masses. It is enough whereas the final core is at least of 0,74   MeV lighter than the initial core so that the weight breakdown of the orbital electron capture opens this way. However, the density of the atomic electrons is low on a nuclear scale, and above the threshold, disintegration β ⁺ becomes dominant.

See too

• Radioactivity β

Random links:

Afgano | Montou | Grosrouvres | Luizinho | Scye | Amiina | York

© 2007-2008 speedlook.com; article text available under the terms of GFDL, from fr.wikipedia.org