In contrast to the most simple radiometric dating techniques, isochron dating, which can be used for many isotopic decay sequences (e.g.
rubidium-strontium decay sequence), does not require knowledge of the initial proportions.
In this case, usually the half-life reported is the dominant (longest) for the entire chain, rather than just one step in the chain.
Nuclides useful for radiometric dating have half-lives ranging from a few thousand to a few billion years.
In most cases, the half-life of a nuclide depends solely on its nuclear properties; it is not affected by temperature, chemical environment, magnetic and electric fields, or any other external factors.
The half-life of any nuclide is also believed to be constant through time.
Radiometric dating is a technique used to date materials based on a knowledge of the decay rates of naturally occurring isotopes, and the current abundances.
While the moment in time at which a particular nucleus decays is random, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life, usually given in units of years when discussing dating techniques.Although decay can be accelerated by radioactive bombardment, such bombardment tends to leave evidence of its occurrence.Therefore, in any material containing a radioactive nuclide, the proportion of the original nuclide to its decay product(s) changes in a predictable way as the original nuclide decays.Mass spectrometers are liable to interferences and inaccuracies.Primary amongst these is the quality of the vacuum.
In the ideal case, the material will incorporate a parent nuclide and reject the daughter nuclide.