Radioactive dating after 2 half lives
In most cases, the energy emitted will be in the form of an X-ray.
Like positron emission, electron capture occurs for “proton-rich” nuclei that lie below the band of stability.
To perform a PET scan, a positron-emitting radioisotope is produced in a cyclotron and then attached to a substance that is used by the part of the body being investigated.
This “tagged” compound, or radiotracer, is then put into the patient (injected via IV or breathed in as a gas), and how it is used by the tissue reveals how that organ or other area of the body functions. A PET scanner (a) uses radiation to provide an image of how part of a patient’s body functions.
Electron capture occurs when one of the inner electrons in an atom is captured by the atom’s nucleus.
For example, potassium-40 undergoes electron capture: Electron capture occurs when an inner shell electron combines with a proton and is converted into a neutron.
Beta (β) decay is the emission of an electron from a nucleus.
We now know that α particles are high-energy helium nuclei, β particles are high-energy electrons, and γ radiation compose high-energy electromagnetic radiation.The radiation produced during radioactive decay is such that the daughter nuclide lies closer to the band of stability than the parent nuclide, so the location of a nuclide relative to the band of stability can serve as a guide to the kind of decay it will undergo (Figure 1). A nucleus of uranium-238 (the parent nuclide) undergoes α decay to form thorium-234 (the daughter nuclide).The alpha particle removes two protons (green) and two neutrons (gray) from the uranium-238 nucleus.Whether electron capture or positron emission occurs is difficult to predict.The choice is primarily due to kinetic factors, with the one requiring the smaller activation energy being the one more likely to occur.