Determination of absolute H atom concentrations in low-pressure flames by two-photon laser-excited fluorescence

Bittner, Jürgen; Kohse‐Höinghaus, Katharina; Meier, Ulrich; Kelm, S.; Just, Th.

doi:10.1016/0010-2180(88)90104-6

Cited by 48 publications

(27 citation statements)

References 20 publications

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“…N-atom concentrations in a discharge flow reactor in a similar way as used before H-and O-atom experiments [4]. For the calibration, the fluorescence intensities in the flame and the flow reactor, IF and lR, were measured under identical excitation and detection conditions, The N-atom concentration in the flow reactor, NR, was determined by gas-phase titration with NO.…”

Section: Methodsmentioning

confidence: 99%

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Determination of N-atom concentrations in low-pressure premixed H2/O2/N2 flames doped with NH3, HCN and (CN)2

Lawitzki¹,

Bittner²,

Kohse‐Höinghaus³

1990

Chemical Physics Letters

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Spatially resolved N-atom concentration and temperature profiles were measured in several stoichiometric, flat, premixed, lowpressure HJ02/Nz flames doped with small amounts of N-containing fuels. Temperature was obtained from OH (A *Z+-X %, I-O) excitation spectra. N atoms were detected by twophoton laser-induced fluorescence, exciting the 3p 4D9,2 state near 211 nm and monitoring the (3p "Do-3s 'P) transition near 870 nm. N-atom concentrations were determined with the aid of a calibration technique using known atom concentrations in a discharge flow reactor and previously determined quenching coefficients. In the flames, peak N-atom mole fractions ranged from about 3 to 90 ppm.

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Section: Methodsmentioning

confidence: 99%

“…Spatially resolved measurement of light-atom concentrations in flames is possible with two-photon laser-induced fluorescence. Numerous publications have reported the detection of H and 0 atoms by these techniques [ 3,4]. N atoms, being far less abundant in flames, have been studied primarily in flow reactors [ 5,6].…”

Section: Introductionmentioning

confidence: 99%

Determination of N-atom concentrations in low-pressure premixed H2/O2/N2 flames doped with NH3, HCN and (CN)2

Lawitzki¹,

Bittner²,

Kohse‐Höinghaus³

1990

Chemical Physics Letters

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mentioning

confidence: 99%

“…Various multi-photon excitation techniques have been used to detect hydrogen and oxygen atoms in flames [13][14][15][16][17][18]. In our group, we have recently developed a calibration method which allows spatially resolved measurements of H and O atom concentrations in low-pressure flames [19,20]. This method relies on a discharge flow reactor as a calibration standard: The two-photon laser-excited fluorescence signal arising from a known atom concentration produced in the flow reactor under identical excitation and detection conditions is related to the fluorescence signal produced by the unknown atom concentration at a particular location in the flame.…”

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Nitrogen atom detection in low-pressure flames by two-photon laser-excited fluorescence

Bittner¹,

Lawitzki²,

Meier³

et al. 1991

Appl. Phys. B

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Abstract. Nitrogen atoms have been detected in stoichiometric flat premixed H2/O2/N2 flames at 33 and 96 mbar doped with small amounts of NH3, HCN, and (CN)2 using two-photon laser excitation at 211 nm and fluorescence detection around 870nm. The shape of the fluorescence intensity profiles versus height above the burner surface is markedly different for the different additives. Using measured quenching rate coefficients and calibrating with the aid of known N-atom concentrations in a discharge flow reactor, peak N-atom concentrations in these flames are estimated to be on the order of 1012-5 × 1013 cm -3 ; the detection limit is about 1 × 1011 cm -3. PACS: 82.40Py, 33.50Dq In the combustion of nitrogen-containing fuels, a variety of conditions have been identified under which atomic nitrogen is of importance. For example, N atoms can influence the product distribution in the conversion of fuelbound nitrogen to N2 or NOx. Depending on the particular nitrogen source and the temperature and equivalence ratio of the combustion process, the reactions of N atoms with e.g. OH, NO, or CH3 can lead to the formation of NO, N2, or HCN. A detailed treatment of the gas-phase nitrogen chemistry in combustion can be found in the recent review by Miller and Bowman [1].Nitrogen atom concentrations have been measured by ESR [2] and by atomic resonance absorption (ARAS) [3]. ESR spectroscopy has been used to detect N atoms in discharge flow reactors [2]. The ARAS technique requires vacuum UV radiation for the detection of N atoms; although it has proven most successful in shock tube experiments [3], flames usually are not transparent for these short wavelengths. Molecular beam sampling techniques coupled with mass spectrometry [4] were used in an investigation of the structure of a 45mbar NH3/O2/Ar flame. In this experiment, N concentrations were found to be below the detection limit (10 .5 ) of the apparatus throughout the flame. Their role in the kinetic mechanism was thus judged to be marginal [4]. The recent kinetic model of [1], however, predicts for this flame a mole fraction of N atoms which is about a factor of 30 higher than the upper limit stated in [4]. Upon addition of small amounts of HCN as N-containing fuel to a 33 mbar H2/O2/Ar flame, Miller etal. [5] find that the NO mole fraction is very sensitive to nitrogen atom reactions. Their conclusions on the importance of N atoms in the processes of NO formation and of conversion of NO to N2 under these conditions are in agreement with earlier work of Haynes [6] and Morley [7]. Although N atoms were not detected in their experiment, Miller et al. [5] predict N atom mole fractions of 5 x 10 .5 to 10 -4 in their flames. In the context of these different flame studies, the bxperimental det'ermination of N atom concentrations for specific combustion situations is expected to provide information which might be used to examine current chemical-kinetic models of the nitrogen chemistry in flames.Two-photon laser-induced fluorescence is a non-perturbing optical diagnostic tech...

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Hydrogen Dissociation at Hot Filaments: Determination of Absolute Atomic Hydrogen Concentrations

Schäfer

Bringmann

Klages

et al. 1991

Diamond and Diamond-Like Films and Coatings

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Determination of absolute H atom concentrations in low-pressure flames by two-photon laser-excited fluorescence

Cited by 48 publications

References 20 publications

Determination of N-atom concentrations in low-pressure premixed H2/O2/N2 flames doped with NH3, HCN and (CN)2

Determination of N-atom concentrations in low-pressure premixed H2/O2/N2 flames doped with NH3, HCN and (CN)2

Nitrogen atom detection in low-pressure flames by two-photon laser-excited fluorescence

Hydrogen Dissociation at Hot Filaments: Determination of Absolute Atomic Hydrogen Concentrations

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