Orbital electron capture

Capture, K-Electron—Electron capture from the K shell by the nucleus of the atom. Also loosely used to designate any orbital electron capture process. 

Normally, in impact ionization, outer electrons are removed. Infrequently, however, an inner electron may be ejected or a K-process may occur such as an orbital electron capture or /3-decay. In such cases, the result is an electronic rearrangement, in preference to emission. Since enough energy is available, frequently the resultant ion is multiply charged. The cross section for this process follows the usual Bethe-type variation -T 1 ln(BT), where B is a constant (Fiquet-Fayard et al., 1968). In charged particle irradiation, the amount of energy lost in the K-processes is very small, usually much less than 1%. On the other hand, some specific effect may be attributable to that that is, experiments can be so designed. 

Es-251 1.5 days Orbital electron capture. Alpha decay... 

When an electron from the nearest orbital i.e., K-shell orbital is absorbed by the nucleus to convert a proton into a neutron without emitting any particle, the process is known as orbital electron capture. Since it is most usually a K-electron which is captured by the nucleus, the process is also known as K-electron capture. Usually an electron from higher energy level L, M, N etc. drop back to fill the vacancy... 

BETA DECAY. The process that occurs when beta particles are emitted by radioactive nuclei. The name beta particle or beta radiation was applied in the early years of radioactivity investigations, before it was fully understood what beta particles are. It is known now, of course, that beta particles are electrons. When a radioactive nuclide undergoes beta decay its atomic number Z changes by +1 or —1, but its mass number A is unchanged. When the atomic number is increased by 1, negative beta particle (negatron) emission occurs and when the atomic number is decreased by 1, there is positive beta particle (position) emission or orbital electron capture. 

Beta Radiation. Beta rays are electrons. They have varying velocities almost up to that of light, The loss of a single negation by an atom leaves the residual atomic nucleus the same in mass number and one unit greater in atomic number, while the loss of a positron or an orbited electron capture leaves the residual atomic nucleus the same in mass number, and one unit less in atomic number. 

Another mode of decay is possible for man-made proton-rich nuclei. It has been shown that certain of such nuclei can capture one of their orbital electrons, lowering the atomic number by one unit and leaving the mass number unchanged. The net change is the same as that in positron decay, but orbital-electron capture or K capture occurs when the mass of the parent atom exceeds that of the daughter atom, but by less than 0.00110 atomic mass unit. A typical example is the conversion of Be7 (mass 7.01916) to Li7 (mass 7.01822) ... 

K-capture. (K-radiation). A type of radioactive decay in which an electron is captured by an atomic nucleus and immediately combines with a proton to form a neutron. The product of this radioactivity has the same mass number as the parent but the atomic number is one unit less. Thus iron with atomic number 26 decays by K-capture to form manganese, with atomic number 25. Terms synonymous with K-capture are K-electron capture and orbital electron capture. 

Decay modes are a = alpha particle emission (B = negative beta emission p+ = positron emission EC = orbital electron capture IT = isomeric transition from upper to lower isomeric state n = neutron emission sf = spontaneous fission (B(B = double beta decay. Total disintegration energy in MeV units. 

Since P decay occurs throughout the periodic table, it offers a wider field of study than a decay, which is largely confined to heavy elements. The term P decay encompasses both P (negatron) and P (positron) emission (Curie and JoKot 1934) as well as the process of orbital electron capture discovered in 1937 (Alvarez 1937) which, like P emission, leads to a one-unit decrease in atomic number. In each of the three processes a neutrino is emitted (in P emission it is an antineutrino). The systematic of P decay has been worked out and selection rules for P transitions in terms of spin and parity changes have been established. Many if not most P transitions lead to excited states of the product nuclei. 

Below the belt of stability, the nuclei have lower neutron-to-proton ratios than those in the belt (for the same number of protons). To increase this ratio (and hence move up toward the belt of stability), these nuclei can decay by either posibon emission decay) or orbital electron capture. For example, potassium-38 (n/p = 19/19 = 1) decays to argon-38 (n/p = 20/18 = 10/9) by positron emission. 

The principal radioactive decay processes are alpha decay, beta decay, gamma emission, and spontaneous fission. Beta decay can occur through the emission of an electron (fi decay) or a positron (fi decay) from the nucleus. Closely related to positron emission is orbital electron capture. 

Note p- = P" = EC = n = negative beta emission positive beta emission orbital electron capture neutron emission ... 

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