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.

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.

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 Absolute Absorption Cross Section of the Ã←X ̃ Electronic Transition of the Ethyl Peroxy Radical and Rate Constant of its Cross Reaction with HO2

2021 ◽  
Author(s):  
Cuihong Zhang ◽  
Mirna Shamas ◽  
Mohamed Assali ◽  
Xiaofeng Tang ◽  
Weijun Zhang ◽  
...  
Keyword(s):  
Cross Section ◽  
Rate Constant ◽  
Absorption Cross Section ◽  
Electronic Transition ◽  
Continuous Wave ◽  
Peroxy Radical ◽  
Cross Reaction ◽  
Peroxy Radicals ◽  
Absorption Cross ◽  
Time Resolved

The absolute absorption cross section of the ethyl peroxy radical, C2H5O2, in the Ã←X ̃ electronic transition with the peak wavelength at 7596 cm-1, has been determined by the method of dual wavelengths time resolved continuous wave cavity ring down spectroscopy. C2H5O2 radicals were generated from pulsed 351 nm photolysis of C2H6/Cl2 mixture in presence of O2 and detected on one of the CRDS paths. Two methods have been applied for the determination of the C2H5O2 absorption cross section: (i) based on Cl-atoms being converted alternatively to either C2H5O2 by adding C2H6 or to hydro peroxy radicals, HO2, by adding CH3OH to the mixture, whereby HO2 was reliably quantified on the second CRDS path in the 21 vibrational overtone at 6638.2 cm-1 (ii) based on the reaction of C2H5O2 with HO2, measured under either excess HO2 or under excess C2H5O2 concentration. Both methods lead to the same peak absorption cross section of C2H5O2,7596 cm-1 = (1.0±0.2) × 10-20 cm2. The rate constant for the cross reaction between of C2H5O2 and HO2 has been measured to be (6.5±1.6) × 10-12 cm3 molecule-1 s-1.

scholarly journals Absolute Absorption Cross-Section of the Ã←X˜ Electronic Transition of the Ethyl Peroxy Radical and Rate Constant of Its Cross Reaction with HO2

Photonics ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 296
Author(s):  
Cuihong Zhang ◽  
Mirna Shamas ◽  
Mohamed Assali ◽  
Xiaofeng Tang ◽  
Weijun Zhang ◽  
...  
Keyword(s):  
Cross Section ◽  
Rate Constant ◽  
Absorption Cross Section ◽  
Electronic Transition ◽  
Continuous Wave ◽  
Peroxy Radical ◽  
Cross Reaction ◽  
Peroxy Radicals ◽  
Absorption Cross ◽  
Time Resolved

The absolute absorption cross-section of the ethyl peroxy radical C2H5O2 in the Ã←X˜ electronic transition with the peak wavelength at 7596 cm−1 has been determined by the method of dual wavelengths time resolved continuous wave cavity ring down spectroscopy. C2H5O2 radicals were generated from pulsed 351 nm photolysis of C2H6/Cl2 mixture in presence of 100 Torr O2 at T = 295 K. C2H5O2 radicals were detected on one of the CRDS paths. Two methods have been applied for the determination of the C2H5O2 absorption cross-section: (i) based on Cl-atoms being converted alternatively to either C2H5O2 by adding C2H6 or to hydro peroxy radicals, HO2, by adding CH3OH to the mixture, whereby HO2 was reliably quantified on the second CRDS path in the 2ν1 vibrational overtone at 6638.2 cm−1 (ii) based on the reaction of C2H5O2 with HO2, measured under either excess HO2 or under excess C2H5O2 concentration. Both methods lead to the same peak absorption cross-section for C2H5O2 at 7596 cm−1 of σ = (1.0 ± 0.2) × 10−20 cm2. The rate constant for the cross reaction between of C2H5O2 and HO2 has been measured to be (6.2 ± 1.5) × 10−12 cm3 molecule−1 s−1.

scholarly journals A new technique for the selective measurement of atmospheric peroxy radical concentrations of HO<sub>2</sub> and RO<sub>2</sub> using denuding method

2009 ◽  
Vol 2 (6) ◽  
pp. 3291-3307 ◽  
Author(s):  
K. Miyazaki ◽  
A. E. Parker ◽  
C. Fittschen ◽  
P. S. Monks ◽  
Y. Kajii
Keyword(s):  
Relative Humidity ◽  
Loss Rate ◽  
Peroxy Radical ◽  
Laser Induced Fluorescence ◽  
Peroxy Radicals ◽  
Atmospheric Measurements ◽  
Absolute Concentrations ◽  
Inlet Conditions ◽  
A New Technique ◽  
No2 Detection

Abstract. A technique for the selective measurement of atmospheric HO2 and RO2 using peroxy radical chemical amplification coupled to laser-induced fluorescence NO2 detection (PERCA-LIF) technique is proposed. By pulling the air through a filled pre-inlet advantage can be taken of the higher heterogeneous loss rate of HO2 relative to CH3O2. Pre-inlet conditions have been found where ca. 90% of HO2 was removed whereas the comparable CH3O2 loss was 15%. The dependence of loss rate on humidity and peroxy radicals' concentration has also been investigated. When using glass beads as the surface for peroxy radical remove, the influence of the relative humidity on the removal efficiency becomes negligible. It may therefore be possible to apply this technique to the measurement of absolute concentrations of solely RO2 as well as the sum of HO2 and RO2. The application of this technique to atmospheric measurements is suggested.

The Influence of Irradiation Temperature on U.V. Induced Defect Creation in Dry Silica

1985 ◽  
Vol 61 ◽  
Author(s):  
R. A. B. Devine ◽  
C. Fiori ◽  
J. Robertson
Keyword(s):  
Oxygen Vacancy ◽  
Peroxy Radical ◽  
Irradiation Temperature ◽  
Threshold Temperature ◽  
Peroxy Radicals ◽  
Oxygen Hole ◽  
Spin Resonance ◽  
Dependent Growth ◽  
Dose Dependent ◽  
Annealing Curve

ABSTRACTElectron spin resonance measurements have been carried out on samples of Suprasil Wl (dry silica) subjected to ultraviolet laser radiation (λ = 248 nm, E = 5 eV/photon). Studies have been made for fixed irradiation temperature (room) variable accumulated ultraviolet dose and fixed accumulated dose (3000 J/cm2) at various irradiation temperatures in the range 110 K to 335 K. Three principal defect centers are observed. Non-bridging oxygen hole centers are created at all temperatures in the range studied with slightly higher efficiency at room temperature (ration 300 K/150 K ∼ 2.5). Comparison of the dose dependent growth curve of the 4.8 eV absorption and its isochronal annealing curve with those for the oxygen hole center clearly identify the origin of the absorption band with this defect. A threshold temperature ∼ 200 K is found for oxygen vacancy creation consistent with results on single crystalline quartz. Post irradiation annealing at 593 K eliminates the vacancy centers and the peroxy radical resonance appears. Its growth as a function of accumulated ultraviolet dose and irradiation temperature supports the hypothesis that peroxy radicals form by the trapping of diffusing, molecular oxygen at the oxygen vacancy center.

scholarly journals Measurement of Atmospheric Dimethyl Sulfide with a Distributed Feedback Interband Cascade Laser

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3216 ◽  
Author(s):  
Shuanke Wang ◽  
Zhenhui Du ◽  
Liming Yuan ◽  
Yiwen Ma ◽  
Xiaoyu Wang ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Dimethyl Sulfide ◽  
Tunable Laser ◽  
Distributed Feedback ◽  
Integration Time ◽  
Laser Absorption Spectroscopy ◽  
Atmospheric Measurements ◽  
Pure Nitrogen ◽  
Laser Absorption ◽  
Interband Cascade Laser

This paper presents a mid-infrared dimethyl sulfide (CH3SCH3, DMS) sensor based on tunable laser absorption spectroscopy with a distributed feedback interband cascade laser to measure DMS in the atmosphere. Different from previous work, in which only DMS was tested and under pure nitrogen conditions, we measured DMS mixed by common air to establish the actual atmospheric measurement environment. Moreover, we used tunable laser absorption spectroscopy with spectral fitting to enable multi-species (i.e., DMS, CH4, and H2O) measurement simultaneously. Meanwhile, we used empirical mode decomposition and greatly reduced the interference of optical fringes and noise. The sensor performances were evaluated with atmospheric mixture in laboratory conditions. The sensor’s measurement uncertainties of DMS, CH4, and H2O were as low as 80 ppb, 20 ppb, and 0.01% with an integration time 1 s, respectively. The sensor possessed a very low detection limit of 9.6 ppb with an integration time of 164 s for DMS, corresponding to an absorbance of 7.4 × 10−6, which showed a good anti-interference ability and stable performance after optical interference removal. We demonstrated that the sensor can be used for DMS measurement, as well as multi-species atmospheric measurements of DMS, H2O, and CH4 simultaneously.

Absolute rate constants for hydrocarbon autoxidation. VI. Alkyl aromatic and olefinic hydrocarbons

1967 ◽  
Vol 45 (8) ◽  
pp. 793-802 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Hydrogen Atom ◽  
Steric Hindrance ◽  
Rate Constants ◽  
Peroxy Radical ◽  
Electron System ◽  
Chain Termination ◽  
The Self ◽  
Hydrogen Atom Abstraction ◽  
Peroxy Radicals ◽  
Absolute Rate

Absolute rate constants have been measured for the autoxidation of a large number of hydrocarbons at 30 °C. The chain-propagating and chain-terminating rate constants depend on the structure of the hydrocarbon and also on the structure of the chain-carrying peroxy radical. With certain notable exceptions which are mainly due to steric hindrance, the rate constants for hydrogen-atom abstraction increase in the order primary < secondary < tertiary; and, for compounds losing a secondary hydrogen atom, the rate constants increase in the order unactivated < acyclic activated by a single π-electron system < cyclic activated by a single Π-system < acyclic activated by two π-systems < cyclic activated by two π-systems. The rate constants for chain termination by the self-reaction of two peroxy radicals generally increase in the order tertiary peroxy radicals < acyclic allylic secondary  [Formula: see text] cyclic secondary  [Formula: see text] acyclic benzylic secondary < primary peroxy radicals < hydroperoxy radicals.

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