text: Heterodimeric diatomic complexes involving a noble gas and a halide, such as xenon chloride, are common in the construction of excimer lasers, which are excimers' most common application. These lasers take advantage of the fact that excimer components have attractive interactions in the excited state and repulsive interactions in the ground state. Emission of excimer molecules is also used as a source of spontaneous ultraviolet light (excimer lamps).
  The molecule pyrene is another canonical example of an excimer that has found applications in biophysics to evaluate the distance between biomolecules.
  In organic chemistry, many reactions occur through an exciplex, for example, those of simple arene compounds with alkenes. The reactions of benzene and their products depicted are a [2+2]cycloaddition to the ortho product (A), a [2+3]cycloaddition to the meta product (B) and the [2+4]cycloaddition to the para product (C) with simple alkenes such as the isomers of 2-butene. In these reactions, it is the arene that is excited.
  As a general rule, the regioselectivity is in favor of the ortho adduct at the expense of the meta adduct when the amount of charge transfer taking place in the exciplex increases.