Experimentally validated Raman Monte Carlo simulation for a cuboid object to obtain Raman spectroscopic signatures for hidden material

Periyasamy, Vijitha and Sil, Sanchita and Dhal, Gagan and Ariese, Freek and Umapathy, Siva and Pramanik, Manojit (2015) Experimentally validated Raman Monte Carlo simulation for a cuboid object to obtain Raman spectroscopic signatures for hidden material. In: JOURNAL OF RAMAN SPECTROSCOPY, 46 (7). pp. 669-676.

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Abstract

In conventional Raman spectroscopic measurements of liquids or surfaces the preferred geometry for detection of the Raman signal is the backscattering (or reflection) mode. For non-transparent layered materials, sub-surface Raman signals have been retrieved using spatially offset Raman spectroscopy (SORS), usually with light collection in the same plane as the point of excitation. However, as a result of multiple scattering in a turbid medium, Raman photons will be emitted in all directions. In this study, Monte Carlo simulations for a three-dimensional layered sample with finite geometry have been performed to confirm the detectability of Raman signals at all angles and at all sides of the object. We considered a non-transparent cuboid container (high density polyethylene) with explosive material (ammonium nitrate) inside. The simulation results were validated with experimental Raman intensities. Monte Carlo simulation results reveal that the ratio of sub-surface to surface signals improves at geometries other than backscattering. In addition, we demonstrate through simulations the effects of the absorption and scattering coefficients of the layers, and that of the diameter of the excitation beam. The advantage of collecting light from all possible 4 angles, over other collection modes, is that this technique is not geometry specific and molecular identification of layers underneath non-transparent surfaces can be obtained with minimal interference from the surface layer. To what extent all sides of the object will contribute to the total signal will depend on the absorption and scattering coefficients and the physical dimensions. Copyright (c) 2015 John Wiley & Sons, Ltd.

Item Type:	Journal Article
Publication:	JOURNAL OF RAMAN SPECTROSCOPY
Publisher:	WILEY-BLACKWELL
Additional Information:	Copy right for this article belongs to the WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords:	Monte Carlo simulation; Raman spectroscopy; photon migration; multiple scattering; explosive detection
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry Division of Electrical Sciences > Electrical Engineering
Date Deposited:	19 Aug 2015 06:05
Last Modified:	19 Aug 2015 06:05
URI:	http://eprints.iisc.ac.in/id/eprint/52152

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