scholarly journals Peroxy radical detection for airborne atmospheric measurements using cavity enhanced absorption spectroscopy of NO<sub>2</sub>

2013 ◽  
Vol 6 (6) ◽  
pp. 9655-9688 ◽  
Author(s):  
M. Horstjann ◽  
M. D. Andrés Hernández ◽  
V. Nenakhov ◽  
A. Chrobry ◽  
J. P. Burrows
Keyword(s):  
Detection Limit ◽  
Chain Length ◽  
Absorption Spectroscopy ◽  
Peroxy Radical ◽  
Inlet Pressure ◽  
Peroxy Radicals ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
A Chain ◽  
Averaging Time

Abstract. Development of an airborne instrument for the determination of peroxy radicals (PeRCEAS – Peroxy Radical Cavity Enhanced Absorption Spectroscopy) is reported. Ambient peroxy radicals (HO2 and RO2, R being an organic chain) are converted to NO2 by adding NO, and are recycled through subsequent reaction with CO and O2, thus forming a chain reaction with an amplification factor called chain length. The concentration of NO2 is measured by continuous-wave cavity ring-down spectroscopy (CRDS) using an extended cavity diode laser at 409 nm. Optical feedback from a V-shaped cavity optimizes resonator transmission and allows for a simple detector set-up. CRDS directly yields absorption coefficients, thus providing NO2 concentrations without additional calibration. The optimum 1σ detection limit is 0.3 ppbv at an averaging time of 40 s and an inlet pressure of 300 mbar, corresponding to a concentration of 2 × 109 molecules cm−3. The calibration of the PeRCEAS chain length at an inlet pressure of 300 mbar yields a value of 120 ± 7. The peroxy radical 1σ detection limit for an averaging time of 120 s and a chain length of 120 is ~3 pptv.

scholarly journals Peroxy radical detection for airborne atmospheric measurements using absorption spectroscopy of NO<sub>2</sub>

2014 ◽  
Vol 7 (5) ◽  
pp. 1245-1257 ◽  
Author(s):  
M. Horstjann ◽  
M. D. Andrés Hernández ◽  
V. Nenakhov ◽  
A. Chrobry ◽  
J. P. Burrows
Keyword(s):  
Detection Limit ◽  
Absorption Spectroscopy ◽  
Continuous Wave ◽  
Optical Feedback ◽  
Peroxy Radical ◽  
Inlet Pressure ◽  
Peroxy Radicals ◽  
Atmospheric Measurements ◽  
A Chain ◽  
Averaging Time

Abstract. Development of an airborne instrument for the determination of peroxy radicals (PeRCEAS – peroxy radical chemical enhancement and absorption spectroscopy) is reported. Ambient peroxy radicals (HO2 and RO2, R being an organic chain) are converted to NO2 in a reactor using a chain reaction involving NO and CO. Provided that the amplification factor, called effective chain length (eCL), is known, the concentration of NO2 can be used as a proxy for the peroxy radical concentration in the sampled air. The eCL depends on radical surface losses and must thus be determined experimentally for each individual setup. NO2 is detected by continuous-wave cavity ring-down spectroscopy (cw-CRDS) using an extended cavity diode laser (ECDL) at 408.9 nm. Optical feedback from a V-shaped resonator maximizes transmission and allows for a simple detector setup. CRDS directly yields absorption coefficients, thus providing NO2 concentrations without additional calibration. The optimum 1σ detection limit is 0.3 ppbv at an averaging time of 40 s and an inlet pressure of 300 hPa. Effective chain lengths were determined for HO2 and CH3O2 at different inlet pressures. The 1σ detection limit at an inlet pressure of 300 hPa for HO2 is 3 pptv for an averaging time of 120 s.

Ultra-sensitive measurement of peroxy radicals by chemical amplification broadband cavity-enhanced spectroscopy

The Analyst ◽  
2016 ◽  
Vol 141 (20) ◽  
pp. 5870-5878 ◽  
Author(s):  
Yang Chen ◽  
Chengqiang Yang ◽  
Weixiong Zhao ◽  
Bo Fang ◽  
Xuezhe Xu ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Peroxy Radical ◽  
Peroxy Radicals ◽  
Enhanced Absorption ◽  
Chemical Amplification ◽  
Amplification Method ◽  
Cavity Enhanced Absorption Spectroscopy

The chemical amplification method is combined with the incoherent broadband cavity-enhanced absorption spectroscopy for peroxy radical measurements.

scholarly journals Application of Near-Infrared Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to the Detection of Ammonia in Exhaled Human Breath

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3686
Author(s):  
Zhifu Luo ◽  
Zhongqi Tan ◽  
Xingwu Long
Keyword(s):  
Detection Limit ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Optical Feedback ◽  
Low Pressure ◽  
High Spectral Resolution ◽  
Trace Gas ◽  
Human Breath ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interference of gases such as CO2 and H2O are approximately eliminated at the same time. With appropriate optical feedback, a fibered distributed feedback (DFB) diode laser emitting at 1531.6 nm is locked to the resonance of a V-shaped cavity with a free spectral range (FSR) of 300 MHz and a finesse of 14,610. A minimum detectable absorption coefficient of αmin = 2.3 × 10−9 cm−1 is achieved in a single scan within 5 s, yielding a detection limit of 17 ppb for NH3 in breath gas at low pressure, and this stable system allows the detection limit down to 4.5 ppb when the spectra to be averaged over 16 laser scans. Different from typical CEAS with a static cavity, which is limited by the FSR in frequency space, the attainable spectral resolution of our experimental setup can be up to 0.002 cm−1 owing to the simultaneous laser frequency tuning and cavity dither. Hence, the absorption line profile is more accurate, which is most suitable for low-pressure trace gas detection. This work has great potential for accurate selectivity and high sensitivity applications in human breath analysis and atmosphere sciences.

scholarly journals Detection of Sulfur Dioxide by Broadband Cavity Enhanced Absorption Spectroscopy (BBCEAS)

2021 ◽  
Author(s):  
Ryan Thalman ◽  
Jaron C. Hansen
Keyword(s):  
Sulfur Dioxide ◽  
Absorption Spectroscopy ◽  
Cross Sections ◽  
Limit Of Detection ◽  
Uv Light ◽  
Broad Band ◽  
Absorption Path Length ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Averaging Time

Abstract. Sulfur dioxide (SO2) is an important precursor for formation of atmospheric sulfate aerosol and acid rain. We present an instrument using Broad Band Cavity Enhanced Absorption Spectroscopy (BBCEAS) for the measurement of SO2 with a minimum limit of detection of 0.6 ppbv using the spectral range 305.5–312 nm and an averaging time of 60 seconds. The instrument consists of high reflectivity mirrors (0.9984 at 310 nm) and a deep UV light source. The effective absorption path length of the instrument is 610 m in a 0.957 m base length. Published reference absorption cross-sections were used to fit and retrieve the SO2 concentrations and were compared to a diluted standard for SO2. The comparison was well correlated, R2 = 0.9985 with a correlation slope of 1.01.

On-chip cavity-enhanced absorption spectroscopy using a white light-emitting diode and polymer mirrors

Lab on a Chip ◽  
2015 ◽  
Vol 15 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Cathy M. Rushworth ◽  
Gareth Jones ◽  
Martin Fischlechner ◽  
Emma Walton ◽  
Hywel Morgan
Keyword(s):  
Absorption Spectroscopy ◽  
White Light ◽  
Microfluidic Chip ◽  
Path Length ◽  
Light Emitting Diode ◽  
Absorption Path Length ◽  
Light Emitting ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
On Chip

We have integrated disposable polymer mirrors within a microfluidic chip to form a multi-pass cell, which increases the absorption path length by a maximum of 28 times, providing micromolar detection limits in a probed volume of 10 nL.

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