This paper examines infrared spectroscopic effects for the standoff detection of an explosive material, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), inkjet printed on an aluminum surface. Results of a spectroscopic study are described, using multiple optical setups. These setups were selected to explore how variations in the angles of incidence and collection from the surface of the material result in corresponding variations in the spectral signatures. The goal of these studies is to provide an understanding of these spectral changes since it affects standoff detection of hazardous materials on a reflective substrate. We demonstrate that variations in spectral effects are dependent on the relative surface concentration of the deposited RDX. We also show that it is reasonable to use spectroscopic data collected in a standard laboratory infrared spectrometer outfitted with a variable angle reflectometer set at 0° as reference spectra for data collected in a standoff configuration. These results are important to provide a systematic approach to understanding infrared (IR) spectra collection using standoff systems in the field, and to allow for comparison between such data, and data collected in the laboratory. Although the precise results are constrained to a specific material system (thin layers on a reflective substrate), the approach and general discussion provided are applicable to a broad range of IR standoff sensing techniques and applications.
Van NesteC.W.SenesacL.R.ThundatT.“Standoff Spectroscopy of Surface Adsorbed Chemicals”. Anal. Chem. 2009, 81(5): 1952–1956. doi: 10.1021/ac802364e.
3.
LiuX.Van NesteC.W.GuptaM.TsuiY.Y., et al.“Standoff Reflection–Absorption Spectra of Surface Adsorbed Explosives Measured With Pulsed Quantum Cascade Lasers”. Sens. Actuators, B. 2014, 191: 450–456. doi: 10.1016/j.snb.2013.10.026.
4.
MukherjeeA.Von der PortenS.PatelC.K.N.“Standoff Detection of Explosive Substances at Distances of Up to 150 m”. Appl. Opt. 2010, 49(11): 2072–2078. doi: 10.1364/AO.49.002072.
5.
FurstenbergR.KendzioraC.A.StepnowskiJ.StepnowskiS.V., et al.“Stand-Off Detection of Trace Explosives via Resonant Infrared Photothermal Imaging”. Appl. Phys. Lett. 2008, 93(22): 224103 –doi: 10.1063/1.3027461.
6.
C.J. Breshike, C.A. Kendziora, R. Furstenberg, V. Nguyen, R.A. McGill. “Methodology for Using Active Infrared Spectroscopy in Standoff Detection of Trace Explosives”. Proc. SPIE. 10183. 2017. doi: 10.1117/12.2262199.
7.
C.J. Breshike, C.A. Kendziora, Y. Yoon, R. Furstenberg, et al. “Infrared backscatter Imaging Spectroscopy for Standoff Detection of Trace Explosives". Proc. SPIE. 11010. 2019. doi: 10.1117/12.2518951.
8.
J.R. Castro-Suarez, L.C. Pacheco-Londoño, J. Aparicio-Bolaño, S.P. Hernández-Rivera. “Active Mode Remote Infrared Spectroscopy Detection of TNT and PETN on Aluminum Substrates”. J. Spectrosc. 2017. 2730371. doi: 10.1155/2017/2730371.
9.
MartinezR.A.GuoK.ZhaiT.TerryF.L., et al.“Active Mid-Wave to Long-Wave Supercontinuum FT-IR Sensor for Standoff Chemical Detection”. J. Lightwave Technol. 2019, 37(14): 3626–3636. doi: 10.1109/JLT.2019.2918532.
10.
WitinskiM.F.BlanchardR.PflueglC.DiehlL., et al.“Portable Standoff Spectrometer for Hazard Identification Using Integrated Quantum Cascade Laser Arrays from 6.5 to 11 µm”. Opt. Express. 2018, 26(9): 12159–12168. doi: 10.1364/OE.26.012159.
11.
DatskosP.G.Morales-RodriguezM.E.SenesacL.R.“Standoff Imaging of Trace RDX Using Quantum Cascade Lasers”. IEEE Sens. J. 2020, 20(1): 149–154. doi: 10.1109/JSEN.2019.2940883.
12.
F. Fuchs, J.P. Jarvis, S. Hugger, M. Kinzer, et al. “Imaging Standoff Detection of Explosives by Diffuse Reflectance IR Laser Spectroscopy". In: N. Aschenbruck, P. Martini, M. Meier, J. Tölle, editors. Future Security. Berlin; Heidelberg: Springer, 2012. Pp. 388–399.
13.
FuchsF.HuggerS.KinzerM.AidamR., et al.“Imaging Standoff Detection of Explosives Using Widely Tunable Midinfrared Quantum Cascade Lasers”. Opt. Eng. 2010, 49(11): 1–8. doi: 10.1117/1.3506195.
14.
GoyalA.MyersT.WangC.A.KellyM., et al.“Active Hyperspectral Imaging Using a Quantum Cascade Laser (QCL) Array and Digital-Pixel Focal Plane Array (DFPA) Camera”. Opt. Express. 2014, 22(12): 14392–14401. doi: 10.1364/OE.22.014392.
15.
E.R. Deutsch, P. Kotidis, N. Zhu, A.K. Goyal, et al. “Active and Passive Infrared Spectroscopy for the Detection of Environmental Threats". Proc. SPIE. 9106. 2014. doi: 10.1117/12.2058544.
16.
M.E. Morales-Rodríguez, L.R. Senesac, T. Thundat, M.K. Rafailov, P.G. Datskos. “Standoff Imaging of Chemicals Using IR Spectroscopy". Proc. SPIE. 8031. 2011. doi: 10.1117/12.885204.
17.
MajorK.J.ShawL.B.BusseL.GattassR., et al.“Fiber Optic Coupled Quantum Cascade Infrared Laser System for Detection of Explosive Materials on Surfaces”. Opt. Laser Technol. 2019, 119: 105635 –doi: 10.1016/j.optlastec.2019.105635.
18.
K.J. Ewing, K.J. Major, J.S. Sanghera, R.R. Gattass, et al. “Enabling Standoff Detection of Hazardous Materials Using a Fiber Optic Coupled Quantum Cascade Infrared Laser System". Proc. SPIE. 10629. 2018. doi: 10.1117/12.2304352.
19.
F. Fuchs, S. Hugger, J. Jarvis, V. Blattmann, et al. “Infrared Hyperspectral Standoff Detection of Explosives". Proc. SPIE. 8710. 2013. doi: 10.1117/12.2015682.
20.
C.J. Breshike, C.A. Kendziora, R. Furstenberg, V. Nguyen, et al. “A System for Rapid Chemical Identification Based on Infrared Signatures". Proc. SPIE. 10639. 2018. doi: 10.1117/12.2304435.
21.
P. Kotidis, E.R. Deutsch, A. Goyal. “Standoff Detection of Chemical and Biological Threats Using Miniature Widely Tunable QCLs". Proc. SPIE. 9467. 2015. doi: 10.1117/12.2178169.
W. Ortiz-Rivera, L.C. Pacheco-Londoño, J.R. Castro-Suarez, H. Felix-Rivera, S.P. Hernandez-Rivera. “Vibrational Spectroscopy Standoff Detection of Threat Chemicals". Proc. SPIE. 8031. 2011. doi: 10.1117/12.884433.
24.
J.R. Castro-Suarez, L.C. Pacheco-Londoño, W. Ortiz-Rivera, M. Vélez-Reyes, et al. “Open Path FT-IR Detection of Threat Chemicals in Air and on Surfaces". Proc. SPIE. 8012. 2011. doi: 10.1117/12.884436.
25.
López-LópezM.García-RuizC.“Infrared and Raman Spectroscopy Techniques Applied to Identification of Explosives”. TrAC, Trends Anal. Chem. 2014, 54: 36–44. doi: 10.1016/j.trac.2013.10.011.
26.
SuterJ.D.BernackiB.PhillipsM.C.“Spectral and Angular Dependence of Mid-Infrared Diffuse Scattering from Explosives Residues for Standoff Detection Using External Cavity Quantum Cascade Lasers”. Appl. Phys. B: Lasers Opt. 2012, 108(4): 965–974. doi: 10.1007/s00340-012-5134-2.
27.
EmmonsE.D.FarrellM.E.HolthoffE.L.TripathiA., et al.“Characterization of Polymorphic States in Energetic Samples of 1,3,5-Trinitro-1,3,5-triazine (RDX) Fabricated Using Drop-on-Demand Inkjet Technology”. Appl Spectrosc. 2012, 66(6): 628–635. doi: 10.1366/12-06608.
28.
MesserschmidtR.G.“Complete Elimination of Specular Reflectance in Infrared Diffuse Reflectance Measurements”. Appl. Spectrosc. 1985, 39(4): 737–739.
29.
KarpowiczR.J.SergioS.T.BrillT.B.“β-Polymorph of Hexahydro-1,3,5-trinitro-s-triazine. A Fourier Transform Infrared Spectroscopy Study of an Energetic Material”. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22(2): 363–365. doi: 10.1021/i300010a038.
30.
Guadarrama-PérezC.Martínez de La HozJ.M.BalbuenaP.B.“Theoretical Infrared and Terahertz Spectra of an RDX/Aluminum Complex”. J. Phys. Chem. A. 2010, 114(6): 2284–2292. doi: 10.1021/jp909976d.
31.
Infante-CastilloR.Pacheco-LondoñoL.C.Hernández-RiveraS.P.“Monitoring the α→β Solid–Solid Phase Transition of RDX with Raman Spectroscopy: A Theoretical and Experimental Study”. J. Mol. Struct. 2010, 970(1): 51–58. doi: 10.1016/j.molstruc.2010.02.021.
32.
YuanJ.JiG.ChenX.WeiD., et al.“Phase Transition, Thermodynamics Properties and IR Spectrum of α- and γ-RDX: First Principles and MD Studies”. Chem. Phys. Lett. 2016, 644: 250–254. doi: 10.1016/j.cplett.2015.11.062.
33.
Figueroa-NavedoA.M.Ruiz-CaballeroJ.L.Pacheco-LondoñoL.C.Hernández-RiveraS.P.“Characterization of α- and β-RDX Polymorphs in Crystalline Deposits on Stainless Steel Substrates”. Cryst. Growth Des. 2016, 16(7): 3631–3638. doi: 10.1021/acs.cgd.6b00078.
34.
T.A. Blake, T.J. Johnson, R.G. Tonkyn, B.M. Forland, et al. “Quantitative Total and Diffuse Reflectance Laboratory Measurements for Remote, Standoff, and Point Sensing". Proc. SPIE. 9073. 2014. doi: 10.1117/12.2054116.
35.
L.C. Pacheco-Londoño, J.R. Castro-Suarez, J.A. Aparicio-Bolaños, S.P. Hernández-Rivera. “Angular Dependence of Source-Target-Detector in Active Mode Standoff Infrared Detection". Proc. SPIE. 8711. 2013. doi: 10.1117/12.2016153.
36.
WenP.AminM.HerzogW.D.KunzR.R.“Key Challenges and Prospects for Optical Standoff Trace Detection of Explosives”. TrAC, Trends Anal. Chem. 2018, 100: 136–144. doi: 10.1016/j.trac.2017.12.014.
37.
FisherR.A.“Statistical Methods for Research Workers”. In: KotzS.JohnsonN.L. (eds). Breakthroughs in Statistics: Methodology and Distribution., New York: Springer, 1992, pp. 66–70. . doi: 10.1007/978-1-4612-4380-9_6.
38.
BenestyJ.ChenJ.HuangY.CohenI.“Pearson Correlation Coefficient”. In: CohenI.HuangY.ChenJ.BenestyJ. (eds). Noise Reduction in Speech Processing., Berlin; Heidelberg: Springer, 2009, pp. 1–4. . doi: 10.1007/978-3-642-00296-0_5.
39.
PressW.H.TeukolskyS.A.VetterlingW.T.FlanneryB.P.Numerical Recipes in C: The Art of Scientific Computing., Cambridge: Cambridge University Press, 1992.
J.N. Sweet. “The Spectral Similarity Scale and its Application to the Classification of Hyperspectral Remote Sensing Data". Published in: IEEE Workshop on Advances in Techniques for Analysis of Remotely Sensed Data, 2003. Greenbelt, Maryland; 27–28 October 2003. Piscataway, NJ: IEEE. Pp. 92–99. doi: 10.1109/WARSD.2003.1295179.
