Editing Carbon-14 (section)

==Radioactive decay and detection==
Carbon-14 undergoes [[beta decay]]:

:{{chem|14|6|C}} → {{chem|14|7|N}} + {{chem2|e-}} + {{subatomic particle|electron antineutrino}} + 0.156.5 MeV

By emitting an [[electron]] and an [[electron antineutrino]], one of the neutrons in carbon-14 decays to a proton and the carbon-14 ([[half-life]] of {{val|5,700|30}} years{{NUBASE2020|ref}}) decays into the stable (non-radioactive) isotope [[nitrogen-14]].

As usual with beta decay, almost all the decay energy is carried away by the beta particle and the neutrino. The emitted beta particles have a maximum energy of about 156 keV, while their weighted mean energy is 49&nbsp;keV.<ref name="Nicols-2011">{{cite web| vauthors = Nicols AL |title=14C Comments on evaluation of decay data|url=http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_com.pdf|website=www.nucleide.org|publisher=LNHB|access-date=30 October 2021|url-status=live|archive-url=https://web.archive.org/web/20110815171408/http://www.nucleide.org:80/DDEP_WG/Nuclides/Tl-208_com.pdf |archive-date=2011-08-15 }}</ref> These are relatively low energies; the maximum distance traveled is estimated to be 22&nbsp;cm in air and 0.27&nbsp;mm in body tissue. The fraction of the radiation transmitted through the [[Stratum lucidum|dead skin layer]] is estimated to be 0.11. Small amounts of carbon-14 are not easily detected by typical [[Geiger–Müller tube|Geiger–Müller (G-M) detectors]]; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 decays per minute (0.05&nbsp;μCi). [[Liquid scintillation counting]] is the preferred method<ref>{{cite book | chapter-url = http://web.princeton.edu/sites/ehs/radmanual/radman_app_b.htm#c14 | title = Radiation Safety Manual for Laboratory Users | chapter = Appendix B: The Characteristics of Common Radioisotopes | archive-url = https://web.archive.org/web/20131002005809/http://web.princeton.edu/sites/ehs/radmanual/radman_app_b.htm | archive-date=2013-10-02 | publisher = Princeton University }}</ref> although more recently, accelerator mass spectrometry has become the method of choice; it counts all the carbon-14 atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly. The G-M counting efficiency is estimated to be 3%. The half-distance layer in water is 0.05&nbsp;mm.<ref>{{cite web | url = http://www.oseh.umich.edu/radiation/c14.shtml | work = Material Safety Data Sheet. | title = Carbon-14 | archive-url = https://web.archive.org/web/20130312103041/http://www.oseh.umich.edu/radiation/c14.shtml | archive-date=2013-03-12 | publisher = University of Michigan }}</ref>