Editing Excimer (section)

==Examples and use==
{| class="wikitable" style="float:right"
|+ Excimer lasers
|-
! Laser !! Reagents !! Emission peak
|-
| [[Xenon chloride laser|XeCl]] || {{chem2|Xe + Cl2}} || 308&nbsp;nm
|-
| [[Krypton fluoride laser|KrF]] || {{chem2|Kr + NF3}} || 248&nbsp;nm
|-
| [[Argon fluoride laser|ArF]] || {{chem2|Ar + F2}} || 193&nbsp;nm
|}
Heterodimeric diatomic complexes involving a [[noble gas]] and a [[halide]], such as [[xenon monochloride|xenon chloride]], are common in the construction of [[excimer laser]]s, 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 state|repulsive interactions]] in the [[ground state]]. Emission of excimer molecules is also used as a source of spontaneous ultraviolet light ([[excimer lamp]]s).<ref>{{cite journal |doi=10.1070/PU2003v046n02ABEH001308|title=Excilamps: Efficient sources of spontaneous UV and VUV radiation|year=2003|last1=Lomaev|first1=Mikhail I.|last2=Skakun|first2=V. S.|last3=Sosnin|first3=E. A.|last4=Tarasenko|first4=Viktor F.|last5=Shitts|first5=D. V.|last6=Erofeev|first6=M. V.|journal=Physics-Uspekhi|volume=46|issue=2|pages=193–209}}</ref>

The molecule [[pyrene]] is another canonical example of an excimer that has found applications in [[biophysics]] to evaluate the distance between [[biomolecules]].<ref>{{cite journal |doi=10.1038/nsb986|pmid=14502269|title=Myosin cleft movement and its coupling to actomyosin dissociation|year=2003|last1=Conibear|first1=Paul B.|last2=Bagshaw|first2=Clive R.|last3=Fajer|first3=Piotr G.|last4=Kovács|first4=Mihály|last5=Málnási-Csizmadia|first5=András|journal=Nature Structural & Molecular Biology|volume=10|issue=10|pages=831–835|hdl=2381/134|url=https://figshare.com/articles/journal_contribution/10078475 |hdl-access=free}}</ref>

In [[organic chemistry]], many reactions occur through an exciplex, for example, those of simple [[arene compound]]s with alkenes.<ref>{{cite journal |doi=10.1002/anie.200603337|pmid=17143914|title=Photochemistry of Arenes—Reloaded|year=2007|last1=Mattay|first1=Jochen|journal=Angewandte Chemie International Edition|volume=46|issue=5|pages=663–665}}</ref> The reactions of [[benzene]] and their products depicted are a [2+2]cycloaddition to the [[Arene substitution patterns#Ortho.2C meta.2C and para substitution|ortho product]] (A),<ref>{{cite patent|country=US|status=patent|number=2805242|title=1-cyanobicyclo [4.2.0] octa-2, 4-dienes and their synthesis|gdate=1957-09-03|invent1=Ayer|inventor1-first=Donald|invent2=Buchi|inventor2-first=George}}</ref> a [2+3]cycloaddition to the [[Arene substitution patterns#Ortho.2C meta.2C and para substitution|meta product]] (B)<ref>{{cite journal |doi=10.1021/ja00961a052|title=A Photochemical 1,3 Cycloaddition of Olefins to Benzene1|year=1966|last1=Wilzbach|first1=K. E.|last2=Kaplan|first2=Louis|journal=Journal of the American Chemical Society|volume=88|issue=9|pages=2066–2067|bibcode=1966JAChS..88.2066W }}</ref> and the [2+4]cycloaddition to the [[Arene substitution patterns#Ortho.2C meta.2C and para substitution|para product]] (C)<ref>{{cite journal|doi=10.1021/ja00737a052|title=Photoaddition of benzene to olefins. II. Stereospecific 1,2 and 1,4 cycloadditions|year=1971|last1=Wilzbach|first1=Kenneth E.|last2=Kaplan|first2=Louis|journal=Journal of the American Chemical Society|volume=93|issue=8|pages=2073–2074|bibcode=1971JAChS..93.2073W }}</ref> with simple alkenes such as the isomers of [[2-butene]]. In these reactions, it is the arene that is excited.

[[Image:Arenephotocycloadditions.svg|400px|center|Arene photocycloadditions]]

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.