Non‐intrusive <i>in situ</i> detection of methyl chloride in hot gas flows using infrared degenerate four‐wave mixing

Sahlberg, Anna Lena; Zhou, Jianfeng; Aldén, Marcus; Li, Zhongshan

doi:10.1002/jrs.4651

Cited by 13 publications

(23 citation statements)

References 24 publications

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“…In the IR‐DFWM simulation in this paper, an S 2 ∝ μ 4 dependence of the signal was assumed in accord with Farrow and Rakestraw . This dipole moment dependence has previously been shown as a good representation of the IR‐DFWM signal for similar laser intensities . An empirical Voigt profile was used in the simulations with parameters chosen to match the observed experimental line shapes.…”

Section: Methodsmentioning

confidence: 99%

“…Extensive theoretical and numerical simulations would be needed to fully simulate the IR‐DFWM spectra of these molecules, which is outside the scope of this article. In this article, the IR‐DFWM spectra were instead simulated using data from the HITRAN database and an empirical formula, where the IR‐DFWM signal is simulated by

I_{DFWM} \propto N^{2} σ {(ν)}^{2}

σ ( ν ) is the absorption cross section for wavenumber ν , which is calculated as

σ ((), ν) = true \underset{i}{true\sum} S_{i} g ((), ν)

where S i ∝ μ 2 is the line intensity for transition i given in the HITRAN database and g ( ν ) is the line shape of the transitions. In the IR‐DFWM simulation in this paper, an S 2 ∝ μ 4 dependence of the signal was assumed in accord with Farrow and Rakestraw .…”

Section: Methodsmentioning

confidence: 99%

“…The IR‐DFWM signals for lines containing many closely spaced transitions, for example, the P Q 6 line in Fig. , have much higher intensity than the signals from single lines . This enables measurements with more sensitive detection limits even for relatively weak line strength for individual lines and also the possibility of better discrimination against interfering lines due to the high contrast to the background of weak lines in the spectrum.…”

Section: Methodsmentioning

confidence: 99%

“…Sun et al developed a set of IR‐BOXCAR plates for stable and easy alignment of the forward phase‐matching geometry in the mid‐IR . A similar setup has been used for detection of CH 3 Cl in hot gas flows . Dam et al recently introduced a low noise upconversion detector for sensitive and low noise detection of mid‐infrared light, and the detector was reported to greatly enhance the sensitivity of the IR‐DFWM technique …”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of ro‐vibrational spectra of small hydrocarbons at elevated temperatures using infrared degenerate four‐wave mixing

Sahlberg

Zhou

Aldén

et al. 2016

J Raman Spectroscopy

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The ro-vibrational spectra around 3 μm of four small hydrocarbons (C 2 H 2 , CH 4 , C 2 H 6 and C 2 H 4 ) at 296, 550 and 820 K have been investigated using infrared degenerate four-wave mixing (IR-DFWM). The spectra were recorded in gas flows of nitrogen with small admixtures of the hydrocarbons. A fused silica glass tube surrounded by an electric heating wire was used to heat the gas flows. The recorded IR-DFWM spectra are compared with simulations using the spectral information available in the HITRAN database, in order to identify spectral lines. The measurements demonstrate good signal to noise ratio and good sensitivity even at elevated temperatures. Several weak hot lines were detected that are not included in the current database. This paper demonstrates the potential of IR-DFWM for purposes of investigating spectral lines at elevated temperatures, which is often a challenging task with conventional absorption spectroscopy techniques. The possibility of applying IR-DFWM for combustion diagnostics of small hydrocarbons is discussed from the detection limits of the measurements and the potential water line interference. Because of the non-linear nature of the DFWM technique, it provides much higher contrast for strong lines of small molecules over backgrounds of high-density weak lines, which commonly exist in hot gas flows of thermochemical reactions.

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Section: Methodsmentioning

confidence: 99%

I_{DFWM} \propto N^{2} σ {(ν)}^{2}

σ ( ν ) is the absorption cross section for wavenumber ν , which is calculated as

σ ((), ν) = true \underset{i}{true\sum} S_{i} g ((), ν)

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of ro‐vibrational spectra of small hydrocarbons at elevated temperatures using infrared degenerate four‐wave mixing

Sahlberg

Zhou

Aldén

et al. 2016

J Raman Spectroscopy

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show abstract

“…Li et al exploited these transitions using IR‐DFWM. They demonstrated DFWM of water for flame thermometry and developed a method for methyl chloride detection in hot gas flows . The sensitive detection of chlorinated and fluorinated gaseous species is especially important in the context of the combustion and incineration of biomass and waste material, where such species may be emitted to the environment with the exhaust gas.…”

Section: Applications To Gas‐phase and Combustion Systemsmentioning

confidence: 99%

Advances in nonlinear optical spectroscopies: a historical perspective of developments and applications presented at ECONOS

Kiefer

Materny

Moger

et al. 2015

J Raman Spectroscopy

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This article reviews the contributions to the special issues of the annual European Conference on Nonlinear Optical Spectroscopy (ECONOS) since its establishment in 2002. The review does not only highlight the developments of the scientific areas related to nonlinear optical spectroscopy in Europe but also shows how different sub‐fields evolved globally because ECONOS evolved as an international meeting attracting participants from all over the world. Four main topical categories are identified: (1) theoretical and instrumental developments, (2) applications to gas‐phase and combustion systems, (3) applications to condensed phase matter, and (4) development and applications of micro‐spectroscopy methods. Copyright © 2015 John Wiley & Sons, Ltd.

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Laser‐Based Combustion Diagnostics

Wolfrum

Dreier

Ebert

et al. 2016

Encyclopedia of Analytical Chemistry

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In laser spectroscopy, the interaction of light emitted from various types of laser sources – tunable or nontunable in their output frequency – with the atomic or molecular species of interest is used to probe the sample through a variety of spectral responses. In order to perform laser spectroscopy, suitable laser sources must be selected, which meet the requirements of the chosen spectroscopic method. This means that the laser has to provide radiation in the wavelength range of interest, has the appropriate emission characteristics (lineshape), and has a suitable energy to perform the measurements. Further requirements are pulse length (milliseconds to femtoseconds or continuous wave), repetition rate, and beam profile. Nowadays, laser radiation can be generated with most of the required parameters necessary for the respective spectroscopic application, either directly or by generating new radiation frequencies by frequency mixing of one or several laser beams in a nonlinear medium (gas, liquid, or solid). As an example, the most direct interrogation technique is absorption of laser radiation (LAS, laser absorption spectroscopy) by suitable spectroscopically allowed transitions in atoms or molecules, which are known from conventional spectroscopic methods. The increase or decrease in the laser radiation transmitted through the sample is then a measure of the amount of substance probed in the sample, which characteristically absorbs at the required wavelength. Laser light‐scattering methods, elastic (Rayleigh scattering (RS)), and inelastic (spontaneous Raman scattering (SRS)) are other techniques to probe the medium. In the first method, which is not species specific, the density of the medium can be interrogated, whereas the second is able to probe all species with Raman‐active vibration–rotation transitions. There are several advantages in using laser spectroscopy instead of conventional spectroscopic techniques using conventional thermal light sources. The spectral brightness of laser beams is many orders of magnitude higher than that of thermal radiation sources, which correspondingly increase the detection sensitivity of laser spectroscopic techniques. In addition, the small linewidth of the emitted radiation dramatically increases the spectral resolution such that minor details of the spectroscopic branch investigated can be resolved. This enables more quantitative interpretations of all parameters influencing the lineshape and line intensity of the probed transition, and as such the physical and chemical environments of the probed species: temperature, pressure, velocity, chemical species, and so on. It makes laser spectroscopic techniques much more selective than conventional methods, which often are not able to separate closely spaced spectral features from different species. A third advantage of laser spectroscopic techniques is connected with the variable pulse duration and repetition frequency of lasers: the very short pulse lengths can be used successfully to probe the sample within time periods that are short compared to any other physical or chemical time development – flow, chemical reaction, pressure changes, and so on. Finally, the small spatial regions that can be probed by focusing diffraction‐limited laser beams makes laser spectroscopic techniques ideally suited for applications where high spatial resolution is required. All these advantages of laser spectroscopy are beneficial when the various techniques are applied as a diagnostic tool in combustion processes: flames constitute a complex interaction of fast chemistry with flow fields and surfaces, and therefore, a detailed understanding of combustion events often needs in situ, species‐specific optical diagnostics with high spatial and temporal resolution. In many recent applications, laser spectroscopy has become a developed technique that can even be performed by nonlaser specialists. However, numerous laser spectroscopic techniques require detailed theoretical knowledge of the spectroscopy underlying the respective technique and the use of sophisticated equipment in order to obtain meaningful results. Future development is aimed toward simplifying experimental set‐ups, data evaluation, and maintenance. This development runs parallel to the breathtaking development in laser technology that continuously increases available wavelength ranges, simplicity of use, pulse power, and repetition rates.

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Non‐intrusive in situ detection of methyl chloride in hot gas flows using infrared degenerate four‐wave mixing

Cited by 13 publications

References 24 publications

Investigation of ro‐vibrational spectra of small hydrocarbons at elevated temperatures using infrared degenerate four‐wave mixing

Investigation of ro‐vibrational spectra of small hydrocarbons at elevated temperatures using infrared degenerate four‐wave mixing

Advances in nonlinear optical spectroscopies: a historical perspective of developments and applications presented at ECONOS

Laser‐Based Combustion Diagnostics

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