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A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings

A mobile remote standoff Raman spectroscopy system operational at typical distances of 10 m was developed specifically for research of historical sites and wall paintings recently. Here we present an upgrade to that system informed by a thorough experimental investigation of the relevant laser-induc...

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Autores principales: Li, Yu, Suzuki, Amelia, Cheung, Chi Shing, Gu, Yuda, Kogou, Sotiria, Liang, Haida
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9526390/
https://www.ncbi.nlm.nih.gov/pubmed/36213053
http://dx.doi.org/10.1140/epjp/s13360-022-03305-2
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author Li, Yu
Suzuki, Amelia
Cheung, Chi Shing
Gu, Yuda
Kogou, Sotiria
Liang, Haida
author_facet Li, Yu
Suzuki, Amelia
Cheung, Chi Shing
Gu, Yuda
Kogou, Sotiria
Liang, Haida
author_sort Li, Yu
collection PubMed
description A mobile remote standoff Raman spectroscopy system operational at typical distances of 10 m was developed specifically for research of historical sites and wall paintings recently. Here we present an upgrade to that system informed by a thorough experimental investigation of the relevant laser-induced degradation issues. Reflectance spectroscopy as a more sensitive technique than Raman spectroscopy was used for monitoring and a new phenomenon of reversible alterations was detected in many paint samples at very low laser intensities of less than 1 W/cm(2) when Raman measurements detected no changes. Contrary to conventional wisdom, the intensity threshold for safe operation was found to decrease significantly for larger incident irradiation area in the case of a vermilion oil paint sample. Damage threshold in intensity for each material needs to be determined for different spot sizes, which can be orders of magnitude lower for 1 mm spot size compared with micro-Raman. Results from this study is also relevant to portable Raman systems which use similarly large spot sizes. However, the larger spot size still generates more Raman photons overall under safe operation than micro-Raman systems. Continuous-wave (CW) lasers are found to be best suited to efficient, that is more Raman signal detected over a given measurement time, and safe Raman operation than ns-pulse lasers at the same wavelength. While the damage threshold in intensity for ns-pulse lasers is much higher than that of CW lasers, the pulse energy allowed in one pulse for safe operation is still too low to allow detection of Raman signal, and the need for multiple pulses makes pulse laser inefficient owing to the low repetition rate necessary to ensure adequate heat dissipation between pulses. The safety of the upgraded system was evaluated and found that no permanent laser-induced degradation was detected within 60 s of laser irradiation for any of the paint samples.
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spelling pubmed-95263902022-10-03 A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings Li, Yu Suzuki, Amelia Cheung, Chi Shing Gu, Yuda Kogou, Sotiria Liang, Haida Eur Phys J Plus Regular Article A mobile remote standoff Raman spectroscopy system operational at typical distances of 10 m was developed specifically for research of historical sites and wall paintings recently. Here we present an upgrade to that system informed by a thorough experimental investigation of the relevant laser-induced degradation issues. Reflectance spectroscopy as a more sensitive technique than Raman spectroscopy was used for monitoring and a new phenomenon of reversible alterations was detected in many paint samples at very low laser intensities of less than 1 W/cm(2) when Raman measurements detected no changes. Contrary to conventional wisdom, the intensity threshold for safe operation was found to decrease significantly for larger incident irradiation area in the case of a vermilion oil paint sample. Damage threshold in intensity for each material needs to be determined for different spot sizes, which can be orders of magnitude lower for 1 mm spot size compared with micro-Raman. Results from this study is also relevant to portable Raman systems which use similarly large spot sizes. However, the larger spot size still generates more Raman photons overall under safe operation than micro-Raman systems. Continuous-wave (CW) lasers are found to be best suited to efficient, that is more Raman signal detected over a given measurement time, and safe Raman operation than ns-pulse lasers at the same wavelength. While the damage threshold in intensity for ns-pulse lasers is much higher than that of CW lasers, the pulse energy allowed in one pulse for safe operation is still too low to allow detection of Raman signal, and the need for multiple pulses makes pulse laser inefficient owing to the low repetition rate necessary to ensure adequate heat dissipation between pulses. The safety of the upgraded system was evaluated and found that no permanent laser-induced degradation was detected within 60 s of laser irradiation for any of the paint samples. Springer Berlin Heidelberg 2022-10-01 2022 /pmc/articles/PMC9526390/ /pubmed/36213053 http://dx.doi.org/10.1140/epjp/s13360-022-03305-2 Text en © The Author(s) 2022 https://creativecommons.org/licenses/by/4.0/Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Regular Article
Li, Yu
Suzuki, Amelia
Cheung, Chi Shing
Gu, Yuda
Kogou, Sotiria
Liang, Haida
A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title_full A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title_fullStr A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title_full_unstemmed A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title_short A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings
title_sort study of potential laser-induced degradation in remote standoff raman spectroscopy for wall paintings
topic Regular Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9526390/
https://www.ncbi.nlm.nih.gov/pubmed/36213053
http://dx.doi.org/10.1140/epjp/s13360-022-03305-2
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