Tritium

Tritium, radioactive hydrogen isotope of atomic mass 3 and symbol ₁H³ or T. The nucleus of a tritium atom consists of a proton and two neutrons and has a mass of 3.016049. It undergoes decay by beta emission to give a helium nucleus of mass 3; it has a half-life of 12.26 years. Tritium is produced in a number of ways, including the bombardment of deuterium compounds with high-energy deuterons and by the absorption of neutrons by the lithium isotope of mass 6.

Some tritium is produced in the upper levels of the atmosphere by the bombardment of nitrogen with energetic neutrons produced by cosmic rays; rainwater is usually found to contain minute amounts of tritium. The enormous amount of energy released when tritons react with deuterons in the so-called nuclear-fusion process makes tritium an important constituent of hydrogen bombs (see Nuclear Energy; Nuclear Weapons). Tritium is also used as a tracer in chemical and biochemical research.