Electron capture

Electron Capture

Illustration of electron capture process

Electron capture is a nuclear process in which an atomic nucleus captures one of its own electrons, resulting in the transformation of a proton into a neutron. This process occurs in certain unstable isotopes, leading to the stabilization of the nucleus. Electron capture is an important phenomenon in nuclear physics and has various applications in fields such as astrophysics and medical imaging.

Process

In electron capture, an electron from one of the inner electron shells of an atom is captured by the nucleus. This causes the atomic number of the atom to decrease by one, as a proton is converted into a neutron. The captured electron combines with a proton to form a neutron and a neutrino. The neutrino is emitted from the nucleus, carrying away the excess energy.

The process can be represented by the following equation:

p + e⁻ → n + ν

where p represents a proton, e⁻ represents an electron, n represents a neutron, and ν represents a neutrino.

Significance

Electron capture plays a crucial role in the stability of certain isotopes. It is particularly important in isotopes with a high proton-to-neutron ratio, as it helps to balance the ratio and stabilize the nucleus. This process is commonly observed in isotopes of elements such as potassium, calcium, and iodine.

In astrophysics, electron capture is involved in stellar nucleosynthesis, the process by which elements are formed in stars. It contributes to the synthesis of elements heavier than iron in the late stages of stellar evolution.

In medical imaging, electron capture is utilized in positron emission tomography (PET) scans. In PET scans, a radioactive isotope undergoes electron capture, emitting a positron. The positron then annihilates with an electron, producing two gamma rays that can be detected and used to create detailed images of the internal structures of the body.

Examples

One notable example of electron capture is the decay of potassium-40 (^40K) into argon-40 (^40Ar). ^40K is a radioactive isotope of potassium that undergoes electron capture, transforming a proton into a neutron. This decay process is used in radiometric dating to determine the age of rocks and minerals.

Another example is the decay of iodine-131 (^131I) into xenon-131 (^131Xe). ^131I is commonly used in nuclear medicine for diagnostic and therapeutic purposes. Its decay through electron capture allows for the emission of gamma rays that can be detected and used for imaging and treatment.

See Also

• Nuclear Decay
• Radioactive Isotopes
• Positron Emission Tomography
• Stellar Nucleosynthesis