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Optical reflectance spectroscopy of inhomogeneous materials: Application to ancient documents and textiles.

Missori M.
  Lunedì 12/09   14:00 - 19:00   Aula L - Christa Mc Auliffe   VI - Fisica applicata, acceleratori e beni culturali   Presentazione
Reflectance spectroscopy in the ultraviolet and visible regions, also known as Fiber Optics Reflectance Spectroscopy (FORS), is used to provide qualitative analytical information, in particular for dyes and pigments. Quantitative information, on the other hand, is difficult to obtain for optically inhomogeneous materials characterized by the presence of light scattering. Documents and textiles represent striking examples of this class of materials where it is not possible to obtain a useful absorption spectrum without taking account of light scattering. In this contribution, I will briefly illustrate how to obtain quantitative absorption spectra through FORS by using an integrating sphere and analyzing the reflectance data by means of the Kubelka-Munk theory. For cellulose-based materials, quantitative chemical information on the chromophores responsible for the observed optical degradation is obtained by using time-dependent density functional theory simulations of the optical spectrum of carbonyl groups. Applications to the analysis of Leonardo Da Vinci's drawings, ancient textiles, and monitoring of conservation interventions of paper artworks will be shown.