Editing Nerve agent (section)

==== Laser photoacoustic spectroscopy ====
[[Laser]] [[photoacoustic spectroscopy]] (LPAS) is a method that has been used to detect nerve agents in the air. In this method, laser light is absorbed by [[gaseous]] [[matter]]. This causes a heating/cooling cycle and changes in [[pressure]]. Sensitive [[microphones]] convey [[sound waves]] that result from the pressure changes. Scientists at the [[United States Army Research Laboratory|U.S. Army Research Laboratory]] engineered an LPAS system that can detect multiple trace amounts of toxic gases in one air sample.<ref name="Gurton Felton Tober 2012">{{cite journal |last1=Gurton |first1=Kristan P. |last2=Felton |first2=Melvin |last3=Tober |first3=Richard |title=Selective real-time detection of gaseous nerve agent simulants using multiwavelength photoacoustics |journal=Optics Letters |date=15 August 2012 |volume=37 |issue=16 |pages=3474–3476 |doi=10.1364/OL.37.003474 |pmid=23381295 |bibcode=2012OptL...37.3474G }}</ref>

This [[technology]] contained three lasers [[Modulation|modulated]] to different [[frequency]], each producing a different sound wave tone. The different wavelengths of light were directed into a sensor referred to as the photoacoustic cell. Within the cell were the vapors of different nerve agents. The traces of each nerve agent had a signature effect on the "loudness" of the lasers' sound wave tones.<ref name=":2">{{Cite web|url=https://www.osa.org/en-us/about_osa/newsroom/news_releases/2012/hearing_the_telltale_sounds_of_dangerous_chemicals/|title=Hearing the Telltale Sounds of Dangerous Chemicals: New Photoacoustic Technique Detects Multiple Nerve Agents Simultaneously|last=Meyer|first=Lyndsay|date=August 14, 2012|website=OSA The Optical Society}}</ref> Some overlap of nerve agents' effects did occur in the acoustic results. However, it was predicted that specificity would increase as additional lasers with unique wavelengths were added.<ref name="Gurton Felton Tober 2012"/> Yet, too many lasers set to different [[wavelengths]] could result in overlap of [[absorption spectra]]. Citation LPAS technology can identify [[gases]] in [[parts per billion]] (ppb) concentrations.<ref name="Prasad Lei Shi et al 2012">{{cite book |last1=Prasad |first1=Coorg R. |last2=Lei |first2=Jie |last3=Shi |first3=Wenhui |last4=Li |first4=Guangkun |last5=Dunayevskiy |first5=Ilya |last6=Patel |first6=C. Kumar N. |chapter=Laser photoacoustic sensor for air toxicity measurements |doi=10.1117/12.919241 |editor1-last=Vo-Dinh |editor1-first=Tuan |editor2-last=Lieberman |editor2-first=Robert A. |editor3-last=Gauglitz |editor3-first=Günter |title=Advanced Environmental, Chemical, and Biological Sensing Technologies IX: 26-27 April 2012, Baltimore, Maryland, United States |date=2012 |publisher=SPIE |isbn=978-0-8194-9044-5 }}</ref><ref name=":2" /><ref>{{cite news |last1=Brayboy |first1=Joyce P. |title=Army scientists demonstrate rapid detection of nerve agents |url=https://www.army.mil/article/86656/army_scientists_demonstrate_rapid_detection_of_nerve_agents |work=U.S. Army |agency=U.S. Army Research Laboratory |date=5 September 2012 }}</ref>

The following nerve agent simulants have been identified with this multiwavelength LPAS:<ref name="Gurton Felton Tober 2012"/>

* [[Dimethyl methylphosphonate|dimethyl methyl phosphonate]] (DMMP)
* [[diethyl methyl phosphonate]] (DEMP)
* [[Diisopropyl methylphosphonate|diisopropyl methyl phosphonate]] (DIMP)
* [[dimethylpolysiloxane]] (DIME), triethyl phosphate (TEP)
* [[tributyl phosphate]] (TBP)
* two volatile organic compounds (VOCs)
* [[acetone]] (ACE)
* [[isopropanol]] (ISO), used to construct [[Sarin]] <!---not a nerve agent itself. But can be used to construct Sarin with another chemical mixture--->

Other gases and air contaminants identified with LPAS include:<ref name="Prasad Lei Shi et al 2012"/><ref>{{cite journal |last1=Schmitt |first1=Katrin |last2=Müller |first2=Andreas |last3=Huber |first3=Jochen |last4=Busch |first4=Sebastian |last5=Wöllenstein |first5=Jürgen |title=Compact photoacoustic gas sensor based on broadband IR source |journal=Procedia Engineering |date=2011 |volume=25 |pages=1081–1084 |doi=10.1016/j.proeng.2011.12.266 |doi-access=free }}</ref>

* CO<sub>2</sub> [[Carbon dioxide]]
* [[Benzene]]
* [[Formaldehyde]]
* [[Acetaldehyde]]
* [[Ammonia]]
* NOx [[Nitrogen oxide]]
* SO<sub>2</sub> [[Sulphur oxide]]
* [[Ethylene Glycol]]
* [[TATP]]
* [[TNT]]