Development of methods for studying substances on surfaces by diffuse reflectance spectroscopy and infrared quantum cascade lasers
Dmitriy R. Anfimov1, Igor S. Golyak1, Igor L. Fufurin1, Andrey N. Morozov1; 1Bauman Moscow State University, Moscow, Russia
Abstract
Currently, non-sampling analysis of substances on surfaces in real time is an important task in the domestic instrument industry for countering terrorist threats, drug trafficking and ensuring security. The study of solid and liquid substances on various surfaces using molecular spectroscopy methods is currently carried out, as a rule, based on the effect of Raman scattering (Raman spectroscopy, Raman). This method, although highly selective, has a weak quantum yield, so powerful laser sources are used, which can lead to sample degradation. The work proposes to investigate the possibility of identifying substances on various underlying surfaces using diffusely reflected radiation from a tunable quantum cascade laser with a tuning range of 9.6–12.5 μm. The radiation is collected by two cadmium-mercury-tellurium (CRT) photodetector devices with a detection ability of the order of 8*10^9 cm√Hz/W and an area of 2x2 mm^2. Their combined processing makes it possible to reduce the influence of laser radiation power instability (at least 5% for QCLs in the mid-IR region). In this work, we simulated diffuse reflectance spectra using an ensemble of damped harmonic oscillators (DHO). An increase in the selectivity of the spectra is achieved by converting the experimentally obtained reflectance spectra into transmission spectra using the Kramers-Kronig relations. As part of the work, identification algorithms based on diffuse reflectance spectra have been developed, which will be based on the Pearson correlation method, machine learning and deep learning methods. It is shown that modeling significantly improves the quality of the developed identification algorithms. The developed approach can be used to create modern technical means for analyzing trace amounts on various substrates, which can be used in the food, pharmaceutical, chemical and oil refining industries, as well as in the field of research of cultural heritage sites.
Speaker
Dmitriy Anfimov
Bauman Moscow State Univeristy
Russia
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