Excimer Laser

An excimer laser (sometimes, and more correctly, called an exciplex laser) is a form of ultraviolet chemical laser which is commonly used in eye surgery and semiconductor manufacturing. The term excimer is short for 'excited dimer', while exciplex is short for 'excited complex'. An excimer laser typically uses a combination of an inert gas (Argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). Under the appropriate conditions of electrical stimulation, a pseudo-molecule called a dimer is created, which can only exist in an energized state and can give rise to laser light in the ultraviolet range.
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Excimer laser An instrument that is used to vaporize tissue with a cold, coherent beam of light with a single wavelength in the ultraviolet range. [more]Excimer laser - Community and Resources

The term excimer comes from the combination of excited and dimer. The excimer laser was developed in the late seventies and has output in the ultraviolet and near ultraviolet region. In an excimer laser a noble gas such as krypton, Kr, or xenon, Xe, is excited in the presence of a halogen such as fluorine, F, or chlorine, Cl, and neon, Ne, or helium, He, in a resonant cavity. A high voltage pulse dissociates electrons from the noble gas molecules creating a plasma. In the excited state, noble gas atoms combine with the halogen atoms forming a metastable compound such as KrF or ArF with a lifetime of several nanoseconds. When the electrons in the outer shell of the excited compound are stimulated to a lower energy level, ultraviolet light is emitted and the metastable compound disassociates in a few femtoseconds into the original elements.