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3. Reactions of C2H5 radicals with O, O3, and NO3: decomposition pathways of the intermediate C2H5O radical

Author

Hoyermann, K., Olzmann, M., Seeba, J., and Viskolcz, B.

Subjects
Hydrocarbons -- Analysis, Radicals (Chemistry) -- Research, Decomposition (Chemistry) -- Research, Oxygen -- Research, Nitrates -- Research, Chemicals, plastics and rubber industries
Abstract

The reactions of C2H5 with O, O3 and NO3 were examined in a discharge flow reactor at room temperature and pressures between 1 and 3 mbar. The reaction products were determined by mass spectrometry with electron-impact ionization. The product pattern observed was explained in terms of the decomposition of an intermediately formed, chemically activated ethoxy radical. With this assumption, the experimentally obtained branching ratios of the various product channels can be reproduced almost quantitatively by RRKM computations based on ab initio results for the stationary points of the potential energy surface of C2H5O.

Published
1999

7. CH3 state distributions form the reactions of O(1D) with saturated and chlorinated hydrocarbons.

Author

Schott, R., Schlütter, J., Olzmann, M., and Kleinermanns, K.

Subjects
CARBON, HYDROGEN, CHLOROHYDROCARBONS
Abstract

CH3 product state distributions arising from the reaction of O(1D) with CH4, C2H6, C3H8, and i-C4H10 were characterized using resonantly enhanced multiphoton ionization (REMPI). The vibrational distributions in the ν1 symmetric stretch and in the ν2 ‘‘umbrella’’ mode are noninverted in all cases. The results are compared to statistical adiabatic channel-phase space theory (SACM-PST) calculations. The ν2 excitation is much less excited than statistically expected for the reactions with CH4 and C2H6 but nearly statistical in the case of the heavier hydrocarbons. For all reactions but the one with C2H6, the ν1 excitation is similar to the distribution statistically expected. The CH3 rotational distribution from the reaction of O(1D) with CH4 is much hotter than room temperature as comparison with simulated rotational band contours showed. From the integrated CH3 band intensities, we obtained approximate reaction cross sections for the CH3 channel with a decrease in the order CH3>=C2H6>=C3H8>=i-C4H10. In the reactions of O(1D) with CH3Cl, CH3CH2Cl, and CH3CH2CH2Cl, we observed CH3 as a primary product. CH3–ν1 excitation is small in all cases but ν2 excitation is considerable with even an inverted v=1/v=0 distribution in the case of the reaction with C2H5Cl. The relative reaction cross sections for the CH3 channel decrease in the order CH4>CH3Cl>=CH3CH2Cl>=CH3CH2CH2Cl. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
1995
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30. Determination of the rate coefficient for the C3H3 +C3H3 reaction at high temperatures by shock-tube investigations.

Author

Fernandes, R.X., Hippler, H., and Olzmann, M.

Subjects
ABSORPTION spectra, SHOCK waves, SHOCK tubes, COMBUSTION gases
Abstract

Abstract: The kinetics of the C3H3 +C3H3 reaction was investigated behind incident shock waves at temperatures ranging from 995 to 1440K and at pressures between 600 and 1000mbar with argon as bath gas. The C3H3 radicals were generated by thermal decomposition of propargyl iodide with initial concentrations between 3×1015 and 6×1015 cm?3 corresponding to initial mole fractions between 750 and 800ppm. Measurement of the UV absorption at 332.5nm was used to monitor the C3H3 concentration, and the rate coefficients for the C3H3 +C3H3 reaction were determined by fitting a second-order rate law to the absorption–time profiles. Values between 2×10?11 cm3 s?1 near 1000K and 7.5×10?12 cm3 s?1 near 1400K were obtained with no significant pressure dependence. The negative temperature dependence can be expressed in the form k 1 =5.8×10?13 exp(3534K/T) cm3 s?1 with an estimated maximum error of ±30% in k 1. The reaction channel leading to C6H5 +H is estimated to contribute with less than 10% to the overall reaction at temperatures between 1000 and 1300K and, pressures ranging from 80 to 500mbar. [Copyright &y& Elsevier]

Published
2005
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31. The rate coefficient of the C<SUB>3</SUB>H<SUB>3</SUB> + C<SUB>3</SUB>H<SUB>3</SUB> reaction from UV absorption measurements after photolysis of dipropargyl oxalate

Author

Giri, B. R., Hippler, H., Olzmann, M., and Unterreiner, A. N.

Abstract

The kinetics of the C3H3 + C3H3 reaction was investigated by using dipropargyl oxalate (DPO) as a new, halogen-free photolytic source for propargyl radicals in the gas phase. After laser-flash photolysis of DPO at 193 nm, the initial absorbance was determined at different wavelengths, and the results were compared with values obtained in analogous experiments using propargyl halides as precursors. A satisfactory agreement of the absorbances was found between 295 and 355 nm but differences were observed near 242 nm. The latter wavelength has also been proposed for C3H3 detection. Our results, however, indicate that this absorption is probably due to halogen-containing species. The rate coefficient of the C3H3 + C3H3 reaction was then determined from time-resolved absorption measurements at 332.5 nm with DPO as precursor. Values of (2.7 ± 0.6) × 10−11 cm3 molecule−1 s−1 at 373 K, (2.8 ± 0.6) × 10−11 cm3 molecule−1 s−1 at 425 K, (3.5 ± 0.8) × 10−11 cm3 molecule−1 s−1 at 500 K, and (4.1 ± 0.8) × 10−11 cm3 molecule−1 s−1 at 520 K were obtained with no significant pressure dependence between 1 and ca. 100 bar (140 bar for T = 373 K).

Published
2003

32. The rate coefficient of the C3H3  C3H3reaction from UV absorption measurements after photolysis of dipropargyl oxalate

Author

Giri, B. R., Hippler, H., Olzmann, M., and Unterreiner, A. N.

Abstract

The kinetics of the C3H3  C3H3reaction was investigated by using dipropargyl oxalate DPO as a new, halogen-free photolytic source for propargyl radicals in the gas phase. After laser-flash photolysis of DPO at 193 nm, the initial absorbance was determined at different wavelengths, and the results were compared with values obtained in analogous experiments using propargyl halides as precursors. A satisfactory agreement of the absorbances was found between 295 and 355 nm but differences were observed near 242 nm. The latter wavelength has also been proposed for C3H3detection. Our results, however, indicate that this absorption is probably due to halogen-containing species. The rate coefficient of the C3H3  C3H3reaction was then determined from time-resolved absorption measurements at 332.5 nm with DPO as precursor. Values of 2.7 ± 0.6 × 10−11cm3molecule−1s−1at 373 K, 2.8 ± 0.6 × 10−11cm3molecule−1s−1at 425 K, 3.5 ± 0.8 × 10−11cm3molecule−1s−1at 500 K, and 4.1 ± 0.8 × 10−11cm3molecule−1s−1at 520 K were obtained with no significant pressure dependence between 1 and ca.100 bar 140 bar for T  373 K.

Published
2003
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33. Production of HCl in the OH + ClO Reaction:  Laboratory Measurements and Statistical Rate Theory Calculations

Author

Lipson, J. B., Beiderhase, T. W., Molina, L. T., Molina, M. J., and Olzmann, M.

Abstract

The branching ratio for the OH + ClO reaction has been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. In our earlier study, OD was used instead of OH due to the large HCl background produced by the ClO source (J. Chem. Soc., Faraday Trans. 1997, 93, 2665). Improvements to our experimental technique have significantly reduced this HCl background, thus making it possible to observe directly the production of very small concentrations of HCl (~109 molecule cm-3) from the minor channel of the OH + ClO reaction. At room temperature and ~100 Torr pressure, the rate constant for this minor channel was determined to be (9.5 ± 1.6) × 10-13 cm3 molecule-1 s-1 with a two standard deviation error limit, which remained unchanged when the pressure was increased to 200 Torr. The temperature dependence of the rate constant for this minor channel was also investigated between 207 and 298 K, and the data were fit to the following Arrhenius expression:  (3.2 ± 0.8) × 10-13 exp[(325 ± 60)/T] cm3 molecule-1 s-1. The branching ratio for the HCl channel was determined to be 0.07 ± 0.03 at all pressures and temperatures investigated in this study. Statistical rate theory calculations were also performed on the OH + ClO reaction system and are in good agreement with the experimental results.

Published
1999

41. Zur Rolle nichtthermischer Molekuelpopulationen in der Kinetik atmosphaerenchemischer Reaktionen

Author

Pfeifle, Mark and Olzmann, M.

Subjects
Mastergleichung, Chemistry & allied sciences, ddc:540, Atmosphärenchemie, Statistische Reaktionstheorie, Reaktionskinetik, Chemische Aktivierung
Abstract

Drei atmosphärenchemisch relevante Reaktionen wurden mit Methoden der theoretischen Reaktionskinetik untersucht: die Reaktion von Salpetersäure mit dem Hydroxylradikal, der oxidative Isoprenabbau sowie die Ozonolyse von Cyclohexen. Der Einfluss von nichtthermischen Populationen war von besonderem Interesse. Zur Charakterisierung wurden quantenchemische Rechnungen eingesetzt; die kinetische Beschreibung erfolgte mit Hilfe von Mastergleichungen und der statistischen Reaktionstheorie.

Published
2015
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42. Kinetische Untersuchung der Rolle von Wasserstoffatomen bei der Pyrolyse von 2,5-Dimethylfuran

Author

Friese, Philipp and Olzmann, M.

Subjects
Elementarkinetik, Iodethan, Chemistry & allied sciences, ddc:540, Biokraftstoff, 5-Dimethylfuran
Abstract

Es wurden elementarkinetische Untersuchungen zu Bildung und Verbrauch von Wasserstoffatomen bei der Pyrolyse von 2,5-Dimethylfuran (einem möglichen Biokraftstoff 2. Generation) durchgeführt. Bruttogeschwindigkeitskonstanten und Arrheniusparameter wurden für diese Reaktionen bestimmt. Die Ergebnisse dieser Messungen wurden ausführlich mit der Literatur verglichen.

Published
2013

43. Qualification of the airborne FTIR spectrometer MIPAS-STR and study on denitrification and chlorine deactivation in Arctic winter 2009/10

Author

Woiwode, Wolfgang and Olzmann, M.

Subjects
spectroscopy, chlorine deactivation, denitrification, stratosphere, ddc:500, NATURAL sciences & mathematics
Abstract

This work describes the qualification of the airborne Fourier-Transform infrared spectrometer Michelson Interferometer for Passive Atmospheric Sounding-STRatospheric aircraft (MIPAS-STR) and studies on ozone-relevant processes in the Arctic winter stratosphere. Using MIPAS-STR measurements, correlative in-situ measurements and simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS), the processes denitrification and chlorine deactivation are investigated.

Published
2013

44. Measurements of atmospheric CO2 columns using ground-based FTIR spectra

Author

Dohe, Susanne and Olzmann, M.

Subjects
Earth sciences, ddc:550
Abstract

The investigation of CO2 sources and sinks within the carbon cycle is important in order to understand global climate change. In this work high resolution ground-based FTIR measurements were used to retrieve total column amounts of CO2. Required measures for the reduction of error sources and the improvement of total column accuracies are presented. In addition, a novel analysis procedure to retrieve vertical CO2 profiles from TCCON measurements is shown and validated with in situ measurements.

Published
2013
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45. Kinetische Untersuchungen von Reaktionen kurzlebiger Intermediate im Zündfunken und bei der Verbrennung

Author

Sommerer, Jörg and Olzmann, M.

Subjects
Laserinduzierte Fluoreszenz, Chemistry & allied sciences, ddc:540, Chemische Kinetik, Spektroskopie, Zündfunken, Hydroxyl-Radikale (OH)
Abstract

Der Ablauf von Verbrennungsprozessen wird erheblich durch die Reaktionskinetik kurzlebiger Intermediate bestimmt. Die vorliegende Arbeit beschäftigt sich einerseits mit der Bildungskinetik von CN-Radikalen in Zündfunken, deren Lumineszenz für diagnostische Verfahren herangezogen wird und zum anderen mit den Reaktionen von OH-Radikalen mit den Rußvorläufern Diacetylen und Vinylacetylen. Zur Untersuchung der beiden Teilaspekte kommen spektroskopische Methoden zum Einsatz.

Published
2011
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46. Stoßwellenuntersuchungen und kinetische Modellierungen zur Pyrolyse von Kohlenwasserstoffen und zur Wasserstoffatom-Abstraktion von Cyclohexan

Author

Peukert, Sebastian and Olzmann, M.

Subjects
cyclohexane, Stoßwellenexperimente, kinetics, Chemistry & allied sciences, ddc:540, Shock tube, H abstraction, Reaktionskinetik, Reaktionsmechanismen, Pyrolysen
Abstract

Unter bezüglich Druck und Temperatur verbrennungstechnisch relevanten Bedingungen (1000 K < T < 2000 K; 1.4 bar < p < 2.5 bar) wurde die Pyrolyse von Verbindungen untersucht, die einerseits in Zusammenhang mit der Bildung von Ruß stehen (1,3-Butadien und 2-Butin) und die andererseits als Modelltreibstoff-Komponenten für Kerosinbrennstoffe (Cyclohexan und 1-Hexen) erachtet werden. Auch die Wasserstoffatom-Abstraktion von Cyclohexan wurde untersucht.

Published
2011

47. Stoßwellenuntersuchungen zum Zerfall stickstoffhaltiger Verbindungen mit spektroskopischen Methoden

Author

Busch, Anna and Olzmann, M.

Subjects
Frequenzmodulationsspektroskopie, Chemistry & allied sciences, Mastergleichung, ddc:540, Atomresonanzabsorptionsspektroskopie, Reaktionskinetik, Stoßwellenuntersuchung
Abstract

In dieser Arbeit wurden Geschwindigkeitskonstanten für den thermischen Zerfall von NCN und Allylamin unter verbrennungsrelevanten Bedingungen untersucht. Zerfallsreaktionen stickstoffhaltiger Verbindungen spielen zum Beispiel bei der Stickoxidbildung in Verbrennungsprozessen eine Rolle. Die Experimente wurden an einem Stoßrohr durchgeführt, an das ein ARAS-Aufbau oder ein FM-Spektrometer gekoppelt wurde. Die erhaltenen Ergebnisse wurden mit Hilfe der statistischen Reaktionstheorie analysiert.

Published
2010
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48. Untersuchungen komplexbildender bimolekularer Reaktionen in der Gasphase mit laserspektroskopischen Methoden und statistischer Reaktionstheorie

Author

Kappler, Claudia and Olzmann, M.

Subjects
Laserinduzierte Fluoreszenz, LIF, Chemistry & allied sciences, Mastergleichung, ddc:540, Radikalreaktion, Reaktionskinetik
Abstract

Viele in der Atmosphären- oder Verbrennungschemie wichtige Reaktionen sind komplexbildende bimolekulare Reaktionen. Die Kenntnis ihrer Geschwindigkeitskonstanten ist deshalb für das Verständnis und die Modellierung der komplexen Gesamtprozesse nötig. In dieser Arbeit wurden mit NCN + NO2 und OH + C3H6 Beispiele solcher Reaktionen über einen weiten Parameterbereich mittels Laserphotolyse/LIF experimentell untersucht und die experimentellen Ergebnisse mit statistischer Reaktionstheorie analysiert.

Published
2010
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49. Laserspektroskopische Untersuchungen und molekularkinetische Modellierung der Kinetik von Radikalreaktionen in der Gasphase

Author

Welz, Oliver and Olzmann, M.

Subjects
Gasphase, Laserinduzierte Fluoreszenz, Chemistry & allied sciences, ddc:540, Gehinderte innere Rotation, Statistische Reaktionstheorie, Reaktionskinetik
Abstract

In der vorliegenden Arbeit wurde der thermische Zerfall des Cyclohexoxyradikals sowie die Reaktion von NCN mit NO über einen breiten Parameterbereich untersucht. Es wurden Experimente in quasi-statischen Reaktoren mit Laserphotolyse-/LIF-Technik durchgeführt. Die experimentellen Ergebnisse wurden mit statistischer Reaktionstheorie analysiert. Besondere Bedeutung kam der adäquaten Beschreibung von gehinderten inneren Rotatoren zu, wofür Methoden programmiert, implementiert und getestet wurden.

Published
2009

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