Short-lived species detection of nitrous acid by external-cavity quantum cascade laser based quartz-enhanced photoacoustic absorption spectroscopy

Spectroscopic detection of short-lived gaseous nitrous acid (HONO) at 1254.85 cm−1 was realized by off-beam coupled quartz-enhanced photoacoustic spectroscopy (QEPAS) in conjunction with an external cavity quantum cascade lasers (EC-QCL). High sensitivity monitoring of HONO was performed within a ve...

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Bibliographic Details
Published in:Applied physics letters 2015-03, Vol.106 (10)
Main Authors: Yi, Hongming, Maamary, Rabih, Gao, Xiaoming, Sigrist, Markus W., Fertein, Eric, Chen, Weidong
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
Absorptivity
Air sampling
Applied physics
CALIBRATION
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
CONCENTRATION RATIO
DETECTION
FEEDBACK
Laser applications
LASER CAVITIES
LASER RADIATION
Lasers
MONITORING
NITROUS ACID
NOISE
Organic chemistry
PHOTOACOUSTIC SPECTROSCOPY
Quantum cascade lasers
QUARTZ
SENSITIVITY
SENSORS
Spectrum analysis
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Summary:Spectroscopic detection of short-lived gaseous nitrous acid (HONO) at 1254.85 cm−1 was realized by off-beam coupled quartz-enhanced photoacoustic spectroscopy (QEPAS) in conjunction with an external cavity quantum cascade lasers (EC-QCL). High sensitivity monitoring of HONO was performed within a very small gas-sample volume (of ∼40 mm3) allowing a significant reduction (of about 4 orders of magnitude) of air sampling residence time which is highly desired for accurate quantification of chemically reactive short-lived species. Calibration of the developed QEPAS-based HONO sensor was carried out by means of lab-generated HONO samples whose concentrations were determined by direct absorption spectroscopy involving a ∼109.5 m multipass cell and a distributed feedback QCL. A minimum detection limit (MDL) of 66 ppbv (1 σ) HONO was achieved at 70 mbar using a laser output power of 50 mW and 1 s integration time, which corresponded to a normalized noise equivalent absorption coefficient of 3.6 × 10−8 cm−1 W/Hz1/2. This MDL was down to 7 ppbv at the optimal integration time of 150 s. The corresponding 1σ minimum detected absorption coefficient is ∼1.1 × 10−7 cm−1 (MDL ∼ 3 ppbv) in 1 s and ∼1.1 × 10−8 cm−1 (MDL ∼ 330 pptv) in 150 s, respectively, with 1 W laser power.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4914896