Hydrogen-3 - also known as tritium - is a radioactive isotope of hydrogen that occurs naturally in very small amounts in the atmosphere. It has a half-life of about 12.3 years and beta decays into helium-3. Tritium is used in the nuclear industry as a fuel in nuclear reactors and in the manufacture of nuclear weapons. It can also be used in special phosphors and as a tracer in medical investigations. However, being radioactive also poses certain risks, which limits its use.
The tritium atom consists of a proton - which is specific to H isotopes - and two protons.
See also: list of Hydrogen isotopes.
The atomic nucleus of superheavy hydrogen decays into the stable isotope helium-3, releasing an electron e- and an antineutrino:
T → 3He + e- + ve.
The emitted electron receives an average kinetic energy of 0.0056817(12) MeV (log ft = 3.0524(8)) and the virtually intangible antineutrino 0.012906(3) MeV.
The unusually low energy released here makes the decay of the molecular tritium T2 (ditritium) interesting for experimental measurements of the absolute neutrino mass .
Half-life T½ = 12.32(2) a respectively 3.88524 × 108 seconds s.
|Decay mode||Daughter||Probability||Decay energy||γ energy|
|β-||3He||100 %||0.018592(0) MeV|
Direct parent isotopes are: 4H, 5H.
Tritium is produced, among other things, in nuclear reactors by neutron activation of lithium-6. The reaction takes place in so-called breeding ceramics, from which the gaseous tritium diffuses out.
|Atomic Mass ma||Quantity||Half-life||Spin|
|1.008 u||100 %|
|Isotope 3H||3.01604928132(8) u|
|Isotope 1H||1.0078250322(6) u||99.99 %|
[99.972 - 99.999 %]
|Isotope 2H||2.0141017781(8) u||0.01 %|
[0.001 - 0.028 %]
Nuclear magnetic properties of the NMR active Nuclide 3H
Tritium has the peculiarity that its atomic nucleus responds better to a magnetic field and therefore reacts more sensitively than the proton. Nevertheless, tritium NMR spectroscopy is a niche application: with an isotopic frequency - measured as the proportion of the 3H atom in natural hydrogen - of 10-15%, tritium is practically non-existent available. The availability of tritiated substance is poor; In addition, these chemicals are difficult to handle due to their radioactivity - and handling requires special safety precautions and technical aids. Nevertheless, there are some reports on the practical application of 3H NMR spectroscopy in the specialist literature, as the review article  shows.
The target organ (critical organ) of the radioactive tritium is the entire body. The biological half-life is 19 days.
|OZ||Isotone N = 2||Isobar A = 3|
 - Y.-T. Lin, T. H. Burritt, C. Claessens et al.:
Beta Decay of Molecular Tritium.
In: Physical Review Letters, 124, 222502, (2020), DOI 10.1103/PhysRevLett.124.222502.
 - Leonid B. Krivdin:
Tritium NMR: A compilation of data and a practical guide.
In: MRC, 61(4), 195-247, (2023), DOI 10.1002/mrc.5329.
Last update: 2023-11-28
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