There are several approaches to analyze transmittance data of selenium films, from which one can extract their optical constants and other related topics.<ref>{{Cite journal|last=Jafar|first=Mousa M. Abdul-Gader|last2=Saleh|first2=Mahmoud H.|last3=Ahmad|first3=Mais Jamil A.|last4=Bulos|first4=Basim N.|last5=Al-Daraghmeh|first5=Tariq M.|date=2016-04-01|title=Retrieval of optical constants of undoped amorphous selenium films from an analysis of their normal-incidence transmittance spectra using numeric PUMA method|url=https://link.springer.com/article/10.1007/s10854-015-4156-z|journal=Journal of Materials Science: Materials in Electronics|language=en|volume=27|issue=4|pages=3281–3291|doi=10.1007/s10854-015-4156-z|issn=0957-4522}}</ref>
However, the algebraic method of Swanepoel seems to be trustful and need no dispersion relations in prior, but is limited to transmittance spectra that display a number of peaks (maxima and minima).<ref>{{Cite journal|last=Saleh|first=Mahmoud H.|last2=Ershaidat|first2=Nidal M.|last3=Ahmad|first3=Mais Jamil A.|last4=Bulos|first4=Basim N.|last5=Jafar|first5=Mousa M. Abdul-Gader|date=2017-06-01|title=Evaluation of spectral dispersion of optical constants of a-Se films from their normal-incidence transmittance spectra using Swanepoel algebraic envelope approach|url=https://link.springer.com/article/10.1007/s10043-017-0311-5|journal=Optical Review|language=en|volume=24|issue=3|pages=260–277|doi=10.1007/s10043-017-0311-5|issn=1340-6000}}</ref>
== References ==
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