Sur Terre, il est formé lors de l'absorption de neutrons par les atomes d'azote de la stratosphère et des couches hautes de la troposphère.
Artifacts made from meteorite iron have been found dating from about 5000 BC (and so are about 7000 years old) – for example iron beads in graves in Egypt. Burke, Cosmic Debris: Meteorites in History., 1986, p229, University of California Press.
The purpose of this chapter is to explain the process of radioactive decay and its relationship to the concept of half-life.
The primary intent is to demonstrate how the half-life of a radionuclide can be used in practical ways to “fingerprint” radioactive materials, to “date” organic materials, to estimate the age of the earth, and to optimize the medical benefits of radionuclide usage. Remember that a radionuclide represents an element with a particular combination of protons and neutrons (nucleons) in the nucleus of the atom.
Alpha decay typically occurs in nuclei that are so big that they can’t be stable.
In alpha decay, the nucleus ejects a helium nucleus (alpha particle) composed of two neutrons and two protons, dropping the mass of the original nucleus by four mass units.