Saturated FDFWM lineshapes and intensities: theory and application to quantitative measurements in flames

Attal‐Trétout, Brigitte; Bervas, H.; Taran, J. P.; Boiteux, S. Le; Kelley, Paul; Gustafson, T. K.

doi:10.1088/0953-4075/30/3/008

Cited by 31 publications

(10 citation statements)

References 43 publications

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“…This value is approximately a factor of 60 larger than the line center saturation intensity determined by Williams et al 32 of 0.32 MW/cm 2 for the Q 1 (4) transition of CH excited in the A 2 ⌬ -X 2 ⌸ ͑0,0͒ band in an atmospheric pressure flame. For OH a similar value was obtained by Brown et al 33 for the R 1 (9) transition (I sat ϭ0.72 MW/cm 2 ), whereas Attal et al 2 experimentally determined an effective saturation intensity of 1.8 MW/cm 2 for the Q 1 (6.5) line ͑the line strength ratio, Q 1 :R 1 , for these two branches is ϳ1.5͒, approximately a factor of 10 smaller than our value. In all cited experiments ns-laser pulses were used.…”

Section: A Saturation Of the Pumped Transitionsupporting

confidence: 79%

Rotational level dependence of ground state recovery rates for OH X 2Π(v″=0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique

Tobai

Dreier

Daily

2002

The Journal of Chemical Physics

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Femtosecond degenerate four-wave mixing of carbon disulfide: High-accuracy rotational constants Polarization and probe delay effect on degenerate four wave mixing of pyrazine We report the first direct measurement of the rotational level dependency of the rate of recovery of initially depleted levels in the electronic ground state X 2 ⌸(vЉϭ0) of OH produced in different flame environments at atmospheric pressure. The initial depopulation of a specific rotational level is accomplished by an intense picosecond pump pulse at 308 nm to partially saturate the electronic A 2 ⌺ -X 2 ⌸(0,0) transition. The recovery of the depleted ground state population then is monitored by probing the same level via the ͑1,0͒ band at 283 nm using picosecond degenerate four-wave mixing ͑DFWM͒. Both laser wavelengths were derived from the pulse-amplified and frequency doubled output of two independently tunable distributed feedback dye lasers operated with Rh101 and Rh6G in ethanol, respectively, and pumped with the second harmonic of a frequency doubled ps-Nd:YAG laser. It is shown that the rate of repopulation of the depleted ground state levels decreases by 54% and 50% with increasing rotational quantum number, NЉ, ranging from 2-16 and 2-13 for stoichiometric CH 4 /air and H 2 /O 2 /He flames, respectively. Within experimental error their absolute values in both flames are equal and are not noticeably sensitive to an unequal depletion of the Zeeman sublevels, as created for different polarization configurations of the saturating pump beam and the DFWM probe beams. The rate of (1.8Ϯ0.4)ϫ10 9 s Ϫ1 averaged over all rotational transitions investigated is smaller by a factor of 3 than the corresponding average rate of the temporal DFWM signal intensity decay determined by us previously. The rate also is smaller than total depopulation rates obtained in the excited A 2 ⌺ ϩ state of OH for similar flame conditions.

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Section: A Saturation Of the Pumped Transitionsupporting

confidence: 79%

Rotational level dependence of ground state recovery rates for OH X 2Π(v″=0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique

Tobai

Dreier

Daily

2002

The Journal of Chemical Physics

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“…[3,4,6] Most theoretical studies concerning DFWM assume a monochromatic laser and isolated transitions. [4,16,17] However, a molecular spectrum is often much more complicated, with several closely spaced transitions 'merging' into one absorption line, and these situations are harder to simulate. [9] There have been studies of this theoretical problem of closely spaced absorption lines in DFWM; [18] however, they usually assume the phase conjugate geometry, using UV lasers, and requiring large direct numerical simulation computations.…”

Section: Simulationsmentioning

confidence: 99%

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

Sahlberg

Zhou

Aldén

et al. 2015

J Raman Spectroscopy

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We demonstrate the potential of infrared degenerate four-wave mixing (IR-DFWM) as a tool for non-intrusive in situ spatially resolved detection of CH 3 Cl in reactive hot gas flows especially feasible for applications to biomass combustion and gasification. IR-DFWM spectra of CH 3 Cl, by probing ro-vibrational transitions belonging to the fundamental stretching modes v 1 and v 4 , have been successfully recorded in gas flows diluted with nitrogen at atmospheric pressure and elevated temperatures up to 820 K. In order to identify the spectral lines of CH 3 Cl, the recorded IR-DFWM spectra are compared with simulations using molecular parameters extracted from the HITRAN database. The potential interference from water vapor is discussed from measurements of H 2 O spectrum at 820 K combined with simulations of H 2 O IR-DFWM spectrum based on the HITEMP database, and it was found that the Q Q 6 line of the v 1 band is relatively free from water interference at elevated temperatures. At atmospheric pressure, the detection limits for temperatures at 296, 550 and 820 K were estimated to be 2.1, 3.1 and 6.2 (×10 15 molecules/cm 3 ), respectively, by scanning the Q Q 6 line of the v 1 band. These results show the potential of interference free detection of CH 3 Cl with IR-DFWM in harsh environments like combustion.

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“…Attal-Tretout and co-workers who used a non-perturbative approach to treat pump saturation and atomic motion effects in the FPG which led to modification of the signal lineshapes [60,61]. Their analytical result however was found to work only for unsaturating probes and provided the pumps were not strongly saturating.…”

Section: Analysis Of Dfwm Signals: Practical Considerationsmentioning

confidence: 99%

Laser diagnostics and minor species detection in combustion using resonant four-wave mixing

Kiefer

Ewart

2011

Progress in Energy and Combustion Science

131

112

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Laser-based methods have transformed combustion diagnostics in the past few decades. The high intensity, coherence, high spectral resolution and frequency tunability available from laser radiation has provided powerful tools for studying microscopic processes and macroscopic phenomena in combustion by linear and nonlinear optical processes. This review focuses on nonlinear optical techniques based on resonant four-wave mixing for non-intrusive measurements of minor species in combustion. The importance of minor species such as reaction intermediates is outlined together with the challenges they present for detection and measurement in the hostile environments of flames, technical combustors, and engines. The limitations of conventional optical methods for such measurements are described and the particular advantages of coherent methods using nonlinear optical techniques are discussed.The basic physics underlying four-wave wave mixing processes and theoretical models for signal calculation are then presented together with a discussion of how combustion parameters may be derived from analysis of signals generated in various four-wave mixing processes. The most important four-wave mixing processes, in this context, are then reviewed:Degenerate Four-Wave Mixing (DFWM), Coherent Anti-Stokes Raman Scattering (CARS), Laser Induced Grating Spectroscopy (LIGS) and Polarization Spectroscopy (PS). In each case the fundamental physics is outlined to explain the particular properties and diagnostic advantages of each technique. The application of the methods mentioned to molecular physics studies of combustion species is then reviewed along with their application in measurement of concentration, temperature and other combustion parameters. Related nonlinear techniques and recent extensions to the ultra-fast regime are briefly reviewed. Finally practical considerations relevant to multi-dimensional and multi-species measurements, as well as applications in technical combustion systems are discussed.Keywords: nonlinear optical spectroscopy, four-wave mixing, combustion diagnostics, minor species detection, laser-induced gratings, polarization spectroscopy IntroductionEnergy from renewable sources such as solar and wind power is the goal of much current research and technological development. Combustion, however, is and is likely to remain for the foreseeable future, the most important energy source for heat, electrical power and especially for transportation. In technical combustion systems the chemical energy of fossil fuels such as coal, crude oil and natural gas is converted into heat through oxidation with oxygen from air. However, fossil fuel resources are limited and alternatives like biofuels [1] or novel technologies such as fuel cells [2] are not yet able to meet the demand. Consequently, for a sustainable use of fossil fuels it is desirable to further improve the efficiency, maintainability and reliability of existing combustion devices. Achieving such improvements depends upon an improved understanding of t...

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Saturated FDFWM lineshapes and intensities: theory and application to quantitative measurements in flames

Cited by 31 publications

References 43 publications

Rotational level dependence of ground state recovery rates for OH X 2Π(v″=0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique

Rotational level dependence of ground state recovery rates for OH X 2Π(v″=0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique

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

Laser diagnostics and minor species detection in combustion using resonant four-wave mixing

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