Quenching of two-photon-excited H(3s, 3d) and O(3p 3P2,1,0) atoms by rare gases and small molecules

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

doi:10.1016/0009-2614(88)87068-4

Cited by 161 publications

(83 citation statements)

References 15 publications

(2 reference statements)

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“…The values in our experiment for oxygen are systematically higher by approximately 30% than those communicated in [9]. We find again good agreement for τ Xe , k Xe Xe , and k Xe Ar with values from [11]; the values for k Xe H e , and k Xe Kr are higher by a factor of ≈1.7, however.…”

Section: Natural Lifetimes and Quenching Coefficientssupporting

confidence: 86%

“…For the hydrogen state we find a satisfactory agreement with values from [9,10]. The values in our experiment for oxygen are systematically higher by approximately 30% than those communicated in [9].…”

Section: Natural Lifetimes and Quenching Coefficientssupporting

confidence: 83%

“…O + NO 2 → NO + O 2 k = 9.5 × 10 −12 cm 3 s −1 (9) where k stands for the reaction constant for T = 300 K from [3]. If the reaction path is complete, each reactive molecule leads to the destruction of one atom.…”

Section: Flow-tube Reactormentioning

confidence: 99%

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Absolute calibration of atomic density measurements by laser-induced fluorescence spectroscopy with two-photon excitation

Niemi

Gathen

Döbele

2001

J. Phys. D: Appl. Phys.

281

350

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The two-photon resonances of atomic hydrogen (λ = 2 × 205.1 nm), atomic nitrogen (λ = 2 × 206.6 nm) and atomic oxygen (λ = 2 × 225.6 nm) are investigated together with two selected transitions in krypton (λ = 2 × 204.2 nm) and xenon (λ = 2 × 225.5 nm). The natural lifetimes of the excited states, quenching coefficients for the most important collisions partners, and the relevant ratios of the two-photon excitation cross sections are measured. These data can be applied to provide a calibration for two-photon laser-induced fluorescence measurements based on comparisons with spectrally neighbouring noble gas resonances.

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Section: Natural Lifetimes and Quenching Coefficientssupporting

confidence: 86%

Section: Natural Lifetimes and Quenching Coefficientssupporting

confidence: 83%

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Absolute calibration of atomic density measurements by laser-induced fluorescence spectroscopy with two-photon excitation

Niemi

Gathen

Döbele

2001

J. Phys. D: Appl. Phys.

281

350

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“…Photochemical effects of the 205 nm light on the flame gases 31,35,37 and stimulated emission due to the population inversion in the nϭ1, 2, and 3 levels of atomic hydrogen 38,39 are avoided by decreasing the laser power den-sity. In low pressure environments the collisional quenching of the fluorescence signal can be determined 37,40 and the H LIF signal can be quantified by comparison to measurements in a calibration reactor where the H concentration is known. 29,31,32 At atmospheric pressure, however, quantification of the signal is hampered by collisional quenching of the fluorescence, which not only depends on temperature and pressure, but also on the nature of the collision partners.…”

Section: Introductionmentioning

confidence: 99%

Spatial distributions of atomic hydrogen and C2 in an oxyacetylene flame in relation to diamond growth

Klein-Douwel

Meulen

1998

Journal of Applied Physics

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Two-dimensional laser induced fluorescence measurements are applied to the chemical vapour deposition of diamond by an oxyacetylene flame to visualize the distributions of atomic hydrogen and C 2 in the gas phase during diamond growth. Experiments are carried out in both laminar and turbulent flames and reveal that atomic hydrogen is ubiquitous at and beyond the flame front. Its presence extends to well outside the diamond deposition region, whereas the C 2 distribution is limited to the flame front and the acetylene feather. The diamond layers obtained are characterized by optical as well as scanning electron microscopy and Raman spectroscopy. Clear relations are observed between the local variations in growth rate and quality of the diamond layer and the distribution of H and C 2 in the boundary layer just above the substrate. These relations agree with theoretical models describing their importance in ͑flame͒ deposition processes of diamond. Three separate regions can be discerned in the flame and the diamond layer, where the gas phase and diamond growth are predominantly governed by the flame source gases, the ambient atmosphere, and the interaction of both, respectively.

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“…The most efficient quencher for N (4D°/2) is the water molecule. This was alos noted for quenching of two-photon-excited H (3s, 3d) and O (3p3p2,1,0) atoms [30] where HzO had the largest quenching coefficient of various combustion-relevant collision ~artners. Most quenching coefficients for N atoms, with the exception of the one for CO, are very similar in magnitude to the ones for O atoms, whereas H atoms are quenched about a factor 3-5 faster.…”

Section: Flow Reactor Experimentsmentioning

confidence: 63%

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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Quenching of two-photon-excited H(3s, 3d) and O(3p 3P2,1,0) atoms by rare gases and small molecules

Cited by 161 publications

References 15 publications

Absolute calibration of atomic density measurements by laser-induced fluorescence spectroscopy with two-photon excitation

Absolute calibration of atomic density measurements by laser-induced fluorescence spectroscopy with two-photon excitation

Spatial distributions of atomic hydrogen and C2 in an oxyacetylene flame in relation to diamond growth

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

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