http://en.wikipedia.org/wiki/Radioactive_decayRadioactive decay
Radioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter nuclide. For example: a carbon-14 atom (the "parent") emits radiation and transforms to a nitrogen-14 atom (the "daughter"). This is a stochastic process on the atomic level, in that it is impossible to predict when a given atom will decay, but given a large number of similar atoms the decay rate, on average, is predictable.
http://en.wikipedia.org/wiki/Particle_decayParticle decay is the spontaneous process of one elementary particle transforming into other elementary particles. During this process, an elementary particle becomes a different particle with less mass and an intermediate particle such as W boson in muon decay. The intermediate particle then transforms into other particles. If the particles created are not stable, the decay process can continue.
The process of particle decay is distinct from radioactive decay, in which an unstable atomic nucleus is transformed into a smaller nucleus accompanied by the emission of particles or radiation.
http://en.wikipedia.org/wiki/Self-powered_lightingTritium illumination is the use of gaseous tritium, a radioactive isotope of hydrogen, to create visible light. Tritium regularly emits electrons through beta decay, and when they interact with a phosphor material, fluorescent light is created.
http://en.wikipedia.org/wiki/Self-po...hind_the_lightThe tritium in a gaseous tritium light source undergoes beta decay, releasing electrons which cause the phosphor layer to fluoresce.
During manufacture, a length of borosilicate glass tube which has had the inside surface coated with a phosphor-containing material is filled with the radioactive tritium. The tube is then fused with a CO2 laser at the desired length. Borosilicate is preferred because it is a type of glass noted for its strength and resistance to breakage. In the tube, the tritium gives off a steady stream of electrons due to beta decay. These particles excite the phosphor, causing it to emit a low, steady glow. One could use any beta particle-emitting substance, but in practice tritium is preferred because it is not very hazardous.


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