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Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

TitleTerahertz Absorption by Cellulose: Application to Ancient Paper Artifacts
Publication TypeJournal Article
Year of Publication2017
AuthorsPeccianti, M., Fastampa R., Conte M. A., Pulci O., Violante C., Lojewska J., Clerici M., Morandotti R., & Missori M.

Artifacts made of cellulose, such as ancient documents, pose a significant experimental challenge in the terahertz transmission spectra interpretation due to their small optical thickness. In this paper, we describe a method to recover the complex refractive index of cellulose fibers from the terahertz transmission data obtained on single freely standing paper sheets in the (0.2-3.5)-THz range. By using our technique, we eliminate Fabry-Perot effects and recover the absorption coefficient of the cellulose fibers. The obtained terahertz absorption spectra are explained in terms of absorption peaks of the cellulose crystalline phase superimposed to a background contribution due to a disordered hydrogen-bond network. The comparison between the experimental spectra with terahertz vibrational properties simulated by density-functional-theory calculations confirms this interpretation. In addition, evident changes in the terahertz absorption spectra are produced by natural and artificial aging on paper samples, whose final stage is characterized by a spectral profile with only two peaks at about 2.1 and 3.1 THz. These results can be used to provide a quantitative assessment of the state of preservation of cellulose artifacts.

Date PublishedJUN 15
Type of ArticleArticle
Citation Key ISI:000403362600001