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-functionaltheory 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.

Terahertz absorption by cellulose: application to ancient paper artifacts / Peccianti, M.; Fastampa, Renato; Mosca Conte, A.; Pulci, O.; Violante, ANNA CARMELA; Łojewska, J.; Clerici, M.; Morandotti, R.; Missori, M.. - In: PHYSICAL REVIEW APPLIED. - ISSN 2331-7019. - 7:6(2017). [10.1103/PhysRevApplied.7.064019]

Terahertz absorption by cellulose: application to ancient paper artifacts

FASTAMPA, Renato;VIOLANTE, ANNA CARMELA;
2017

Abstract

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-functionaltheory 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.
2017
Aging; Density functional theory; Hydrogen bonds; Molecular spectra; Van der Waals interaction
01 Pubblicazione su rivista::01a Articolo in rivista
Terahertz absorption by cellulose: application to ancient paper artifacts / Peccianti, M.; Fastampa, Renato; Mosca Conte, A.; Pulci, O.; Violante, ANNA CARMELA; Łojewska, J.; Clerici, M.; Morandotti, R.; Missori, M.. - In: PHYSICAL REVIEW APPLIED. - ISSN 2331-7019. - 7:6(2017). [10.1103/PhysRevApplied.7.064019]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1062375
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