We demonstrate deep ultraviolet (UV) photoacoustic spectroscopy (PAS) of trace explosives using a sensitive microphone at meter standoff distances. We directly detect 10 µg/cm2 of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), and ammonium nitrate (AN) with 1 s accumulations from a 3 m standoff distance. Large PAS signals for standoff detection are achieved by exciting into the absorption bands of the explosives with a 213 nm laser. We also investigate the impact of the deep UV photochemistry of AN on the PAS signal strength and stability. We find that production of gaseous species during photolysis of AN enhances the PAS signal strength. This deep UV photochemistry can, however, limit the PAS signal lifetimes when detecting trace quantities.
GaresK.L.HufzigerK.T.BykovS.V.AsherS.A.“Review of Explosive Detection Methodologies and the Emergence of Standoff Deep UV Resonance Raman”. J. Raman. Spectrosc. 2016; 47(1): 124–141.
2.
KrausaM.ReznevA.A.Vapour and Trace Detection of Explosives for Anti-Terrorism Purposes, Dordrecht, The Netherlands: Kluwer Academic Publishers, 2004.
3.
CaygillJ.S.DavisF.HigsonS.P.J.“Current Trends in Explosive Detection Techniques”. Talanta. 2012; 88: 14–29.
4.
MillerC.J.YoderT.S.“Explosive Contamination from Substrate Surfaces: Differences and Similarities in Contamination Techniques using RDX and C-4”. Sens. Imaging. 2010; 11(2): 77–87.
GottfriedJ.L.De LuciaF.C.MunsonC.A.MiziolekA.W.“Laser-Induced Breakdown Spectroscopy for Detection of Explosives Residues: A Review of Recent Advances, Challenges, and Future Prospects”. Anal. Biochem. Chem. 2009; 395(2): 283–300.
7.
HarrisM.PearsonG.N.WillettsD.V.RidleyK.et al.“Pulsed Indirect Photoacoustic Spectroscopy: Application to Remote Detection of Condensed Phases”. Appl. Opt. 2000; 39(6): 1032–1041.
8.
PierceA.D.“The Wave Theory of Sound”. In: Acoustics: An Introduction to its Physical Principles and Applications, New York: McGraw-Hill, 1981, pp. 1–47.
9.
RosencwaigA.GershoA.“Theory of the Photoacoustic Effect with Solids”. J. Appl. Phys. 1976; 47(1): 64–69.
10.
RosencwaigA.“Theoretical Aspects of Photoacoustic Spectroscopy”. J. Appl. Phys. 1978; 49(5): 2905–2910.
11.
GangulyP.RaoC.N.R.“Photoacoustic Spectroscopy of Solids and Surfaces”. J. Chem. Sci. 1981; 90(3): 153–214.
12.
McDonaldF.A.WetselG.C.Jr. “Generalized Theory of the Photoacoustic Effect”. J. Appl. Phys. 1978; 49(4): 2313–2322.
13.
MarcusL.S.HolthoffE.L.PellegrinoP.M.“Standoff Photoacoustic Spectroscopy of Explosives”. Appl. Spectrosc. 2017; 71(5): 833–838.
14.
NesteC.W.V.SenesacL.R.ThundatT.“Standoff Photoacoustic Spectroscopy”. Appl. Phys. Lett. 2008; 92(23): 234102.
15.
ChenX.GuoD.ChoaF.-S.WangC.-C.et al.“Standoff Photoacoustic Detection of Explosives using Quantum Cascade Laser and an Ultrasensitive Microphone”. Appl. Opt. 2013; 52(12): 2626–2632.
16.
SharmaR.C.KumarD.BhardwajN.GuptaS.et al.“Portable Detection System for Standoff Sensing of Explosives and Hazardous Materials”. Opt. Commun. 2013; 309: 44–49.
17.
LiJ.S.YuB.FischerH.ChenW.et al.“Contributed Review: Quantum Cascade Laser Based Photoacoustic Detection of Explosives”. Rev. Sci. Instrum. 2015; 86(3): 031501.
18.
WynnC.M.HauptR.W.DohertyJ.H.KunzR.R.et al.“Use of Photoacoustic Excitation and Laser Vibrometry to Remotely Detect Trace Explosives”. Appl. Opt. 2016; 55(32): 9054–9059.
CooperJ.K.GrantC.D.ZhangJ.Z.“Experimental and TD-DFT Study of Optical Absorption of Six Explosive Molecules: RDX, HMX, PETN, TNT, TATP, and HMTD”. J. Phys. Chem. A. 2013; 117(29): 6043–6051.
21.
GaresK.L.BykovS.V.GoduguB.AsherS.A.“Solution and Solid Trinitrotoluene (TNT) Photochemistry: Persistence of TNT-like Ultraviolet (UV) Resonance Raman Bands”. Appl. Spectrosc. 2014; 68(1): 49–56.
22.
GaresK.L.BykovS.V.AsherS.A.“UV Resonance Raman Investigation of Pentaerythritol Tetranitrate Solution Photochemistry and Photoproduct Hydrolysis”. J. Phys. Chem. A. 2017; 121(41): 7889–7894.
23.
BykovS.V.MaoM.GaresK.L.AsherS.A.“Compact Solid-State 213 nm Laser Enables Standoff Deep Ultraviolet Raman Spectrometer: Measurements of Nitrate Photochemistry”. Appl. Spectrosc. 2015; 69(8): 895–901.
24.
AsherS.A.TuschelD.D.VargsonT.A.WangL.et al.“Solid State and Solution Nitrate Photochemistry: Photochemical Evolution of the Solid State Lattice”. J. Phys. Chem. A. 2011; 115(17): 4279–4287.
25.
L. Wang, D.D. Tuschel, S.A. Asher. “229 nm UV Photochemical Degradation of Energetic Molecules”. In: Proceedings of the SPIE 8018, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE): Sensing XII, 80181B. 2011. https://doi.org/10.1117/12.887061.
ChenH.DieboldG.“Chemical Generation of Acoustic Waves: A Giant Photoacoustic Effect”. Science. 1995; 270(5238): 963.
28.
HolthoffE.L.FarrellM.E.PellegrinoP.M.“Standardized Sample Preparation Using a Drop-on-Demand Printing Platform”. Sensors. 2013; 13(5): 5814–5825.
29.
StephensonC.C.BentzD.R.StevensonD.A.“The Heat Capacity of Ammonium Nitrate from 15 to 315° K”. J. Am. Chem. Soc. 1955; 77(8): 2161–2164.
30.
KazuhikoI.ToshiyukiM.“The Heat Capacities of Lithium, Sodium, Potassium, Rubidium, and Caesium Nitrates in the Solid and Liquid States”. Bull. Chem. Soc. Jpn. 1983; 56(7): 2093–2100.
31.
CarlingR.W.“Heat Capacities of NaNO3 and KNO3 from 350 to 800 K”. Thermochim. Acta. 1983; 60(3): 265–275.
32.
NagataniM.SeiyamaT.SakiyamaM.SugaH.et al.“Heat Capacities and Thermodynamic Properties of Ammonium Nitrate Crystal: Phase Transitions Between Stable and Metastable Phases”. Bull. Chem. Soc. Jpn. 1967; 40(8): 1833–1844.
33.
BennettD.“A Study of the Thermal Decomposition of Ammonium Nitrate Using a Gas Chromatographic Technique”. J. Chem. Technol. Biotechnol. 1972; 22(9): 973–982.
34.
ThéorêtA.SandorfyC.“Infrared Spectra and Crystalline Phase Transitions of Ammonium Nitrate”. Can. J. Chem. 1964; 42(1): 57–62.
35.
ChellappaR.S.DattelbaumD.M.VelisavljevicN.SheffieldS.“The Phase Diagram of Ammonium Nitrate”. J. Chem. Phys. 2012; 137(6): 064504.
36.
SomasundaramT.GangulyP.RaoC.N.R.“Photoacoustic Investigation of Phase Transitions in Solids”. J. Phys. C. 1986; 19(13): 2137.
37.
Benages-VilauR.CalvetT.Cuevas-DiarteM.A.“Polymorphism, Crystal Growth, Crystal Morphology and Solid-State Miscibility of Alkali Nitrates”. Crystallogr. Rev. 2014; 20(1): 25–55.
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