Radioluminescence luminosity over their working life. The latest generation of radioluminescent materials is based on tritium, a radioactive isotope of hydrogen with half-life of 12.32 years that emits very low-energy beta radiation. It is used on wristwatch faces, gun sights, and emergency exit signs. The tritium gas is contained in a small glass tube, coated with a phosphor on the inside. Beta particles emitted by the tritium strike the phosphor coating and cause it to fluoresce, emitting light, usually yellow-green. Tritium is used because it is believed to pose a negligible threat to human health, in contrast to the previous radioluminescent
Isotopes of hydrogen u) is known as "tritium" and contains one proton and two neutrons in its nucleus. It is radioactive, decaying into helium-3 through β− decay with a half-life of 12.32 years. Trace amounts of tritium occur naturally because of the interaction of cosmic rays with atmospheric gases. Tritium has also been released during nuclear weapons tests. It is used in thermonuclear fusion weapons, as a tracer in isotope geochemistry, and specialized in self-powered lighting devices. The most common method of producing tritium is by bombarding a natural isotope of lithium, lithium-6, with neutrons in a nuclear reactor. Tritium was once used