Excimer

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Commercial 172 nm xenon excirad emitter from the printing industry

The term excimer is an acronym from the short form of " exci ted di mer " ('stimulated dimer '). It is a short-lived particle that consists of two or more connected atoms or molecules . The specialty is that the excimer can only be formed when a binding partner is in an excited state . If this particle loses energy , the binding partners separate and return to the ground state . Light is often emitted here . The emission band is broad and more red-shifted than the emission band of the excited monomer . This property can be used spectroscopically to identify excimers.

By definition, an excimer molecule consists of two or more atoms of the same chemical element . When it comes to atoms of different elements, one speaks of an exciplex . In the literature, however, this fact is seldom taken into account and therefore exciplexes are often incorrectly referred to as excimers.

Use in excimer lasers

In excimer lasers , the properties of excimers (or today mostly exciplexes) are used: the population inversion required for laser technology is already given by the formation of the molecule, since the ground state must not be occupied. The disintegration time is i. A. a few nanoseconds  (ns).

Excimer lasers, which emit in the ultraviolet spectral range, have gained practical importance in medical technology and in photolithography (a field of semiconductor production ). The laser-active medium consists mainly of the following excimers (fluorine) or exciplexes:

See also

literature