Revisiting the liquid mull technique to derive the infrared optical constants of organic powders from transmission IR spectroscopy

Audrey Picard-Lafond; Emmanuela Diaz

doi:10.1117/12.3013495

7 June 2024 Revisiting the liquid mull technique to derive the infrared optical constants of organic powders from transmission IR spectroscopy

Audrey Picard-Lafond, Emmanuela Diaz

Author Affiliations +

Proceedings Volume 13056, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXV; 1305619 (2024) https://doi.org/10.1117/12.3013495
Event: SPIE Defense + Commercial Sensing, 2024, National Harbor, Maryland, United States

Abstract

The determination of the refractive index (n) and extinction coefficient (k) of a compound is a key step for the prediction of its optical properties in different morphological states. For a solid, these optical constants can be obtained experimentally by spectroscopic methods such as ellipsometry and single-angle reflectance spectroscopy. However, in the context of sustaining databases for hyperspectral imaging with the n and k values of hazardous or noxious chemicals, these methods are not always conceivable due to the unobtainability of a single crystal or the hazards associated with heating, ball-milling, grinding and/or pressing the compounds. Hence, exploring a complementary preparation technique holds great interest. To this end, this work revisits the mull technique, which is classically used to perform qualitative FTIR transmission spectroscopy of a powder by trapping it in a mineral oil such as Nujol. By adding gravimetric measurements during sample preparation, this study seeks to provide a quantitative method satisfactory for deriving the absorption coefficient (α) and, consequently, the extinction coefficient (k).

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Audrey Picard-Lafond and Emmanuela Diaz "Revisiting the liquid mull technique to derive the infrared optical constants of organic powders from transmission IR spectroscopy", Proc. SPIE 13056, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXV, 1305619 (7 June 2024); https://doi.org/10.1117/12.3013495

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