Terahertz absorption by cellulose: Application to ancient paper artifacts

Peccianti, M, Fastampa, R, Mosca Conte, A, Pulci, O, Violante, C, Łojewska, J, Clerici, M, Morandotti, R and Missori, M (2017) Terahertz absorption by cellulose: Application to ancient paper artifacts. Physical Review Applied, 7 (6). 064019. ISSN 2331-7019

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Abstract

Artifacts made of cellulose, such as ancient documents, pose a significant experimental challenge in the THz transmission spectra interpretation due to their small optical thickness. In this Letter we describe a method to recover the complex refractive index of cellulose fibers from the THz transmission data obtained on single freely standing paper sheets in the 0.2–3.5 THz range. By using our technique, we were able to eliminate Fabry-Perot effects and recover the absorption coefficient of the cellulose fibers. The obtained THz absorption spectra are explained in terms of absorption peaks of the cellulose crystalline phase superimposed to a background contribution due to a disordered hydrogen bonds network. The comparison between the experimental spectra with THz vibrational properties simulated by density functional theory calculations confirms this interpretation. In addition, evident changes in the THz 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 THz and 3.1 THz. These results could be used to provide a quantitative assessment of the state of preservation of cellulose artifacts.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Sussex Centre for Quantum Technologies
Subjects: Q Science > QC Physics > QC0350 Optics. Light
T Technology > TA Engineering (General). Civil engineering (General) > TA1501 Applied optics. Photonics
Depositing User: Marco Peccianti
Date Deposited: 16 Jun 2017 14:38
Last Modified: 12 Sep 2017 08:12
URI: http://sro.sussex.ac.uk/id/eprint/68665

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Project NameSussex Project NumberFunderFunder Ref
Route to guided TeraHertz backscattering Inspection and Analysis : THEIAG1308EUROPEAN UNIONPCIG14-GA-2013-630833