1. A laser in which a beam of radiation is produced from the transitions in energy levels of ions in a noble gas; such as, helium, neon, argon, krypton, xenon, and radon.
2. A gas laser in which stimulated emission takes place between two energy levels of an ion.

Gases used include argon, krypton, neon, and xenon; examples include helium-cadmium lasers and metal vapor lasers.