Hoyermann, Karlheinz

[["dc.bibliographiccitation.firstpage","8954"],["dc.bibliographiccitation.issue","31"],["dc.bibliographiccitation.journal","Physical Chemistry Chemical Physics"],["dc.bibliographiccitation.lastpage","8968"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Maarfeld, Sven"],["dc.contributor.author","Nacke, Frank"],["dc.contributor.author","Nothdurft, Joerg"],["dc.contributor.author","Olzmann, Matthias"],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Welz, Oliver"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:48:26Z"],["dc.date.available","2018-11-07T08:48:26Z"],["dc.date.issued","2010"],["dc.description.abstract","The kinetics of cycloalkyl + O reactions were studied with respect to their rate coefficients and the product branching ratios from the decomposition of the chemically activated cycloalkoxy radicals. Rate coefficients for the reactions of cyclohexyl (c-C6H11), cycloheptyl (c-C7H13) and cyclooctyl (c-C8H15) radicals with oxygen atoms were determined with an experimental setup consisting of a discharge flow reactor with molecular beam sampling and REMPI/TOF-MS detection. The following rate coefficients were obtained (units: cm(3)/mol(-1) s(-1)): k(c-C6H11 + O) = (1.33 +/- 0.24) x 10(14)(T/298 K)(0.11) (T = 250-600 K), k(c-C7H13 + O) = (1.85 +/- 0.25) x 10(14) (T = 298 K), k(c-C8H15 + O) = (1.56 +/- 0.20) x 10(14)(T/298 K)(0.66+/-0.15) (T = 268-363 K). Stable products were determined by quantitative FTIR spectroscopy. The decomposition of the cycloalkoxy radicals leads besides beta-C-H bond fission (yields: 24% for c-C6H11O, 20-25% for c-C8H15O) mainly to alkyl radicals by ring-opening via beta-C-C bond cleavage. These open-chain alkyl radicals further decompose mainly by beta-C-C bond scission. An increase of the total pressure from 4 mbar to 1 bar had no effect on the product distribution for the reaction c-C6H11 + O, whereas for the reaction c-C8H15 + O further decomposition of the ring-opening product is significantly suppressed at 1 bar. The experimental results on the channel branching and its pressure dependence were rationalized with the statistical rate theory. A comparison of the experimental and modeling results indicates a significant influence of hindered internal rotations (HIRs) on the reactions of the ring-opening products. The harmonic approximation to describe these modes was shown to be inadequate, while a treatment as one-dimensional HIRs led to a significantly improved agreement between experimental and modeling results. Implications of our findings for the formation of secondary organic aerosol and high-temperature combustion are discussed."],["dc.identifier.doi","10.1039/b925920a"],["dc.identifier.isi","000280514800032"],["dc.identifier.pmid","20520884"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21207"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Royal Soc Chemistry"],["dc.relation.issn","1463-9076"],["dc.title","Rate coefficients for cycloalkyl plus O reactions and product branching in the decomposition of chemically activated cycloalkoxy radicals: an experimental and theoretical study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1977"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Physical Chemistry Chemical Physics"],["dc.bibliographiccitation.lastpage","1984"],["dc.bibliographiccitation.volume","7"],["dc.contributor.author","Hack, W."],["dc.contributor.author","Hold, M."],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:46:34Z"],["dc.date.available","2018-11-07T08:46:34Z"],["dc.date.issued","2005"],["dc.description.abstract","The primary products and the rate of the reaction of methyl radicals with oxygen atoms in the gas phase at room temperature have been studied using three different experimental arrangements: ( A) laser. ash photolysis to produce CH3 and O from the precursors CH3I and SO2 (the educts and the products were detected by quantitative FTIR spectroscopy); ( B) the coupling of a conventional discharge flow reactor via a molecular sampling system to a mass spectrometer with electron impact ionization, which allowed the determination of labile and stable species; ( C) laser induced multiphoton ionization combined with a TOF mass spectrometer-molecular beam sampling-flow reactor, which was used for the specific and sensitive detection of the CH3, CD3, C2H5 and C2D5 radicals and the determination of rate coefficients. The branching ratio of the reaction channels was determined by the experimental arrangements (A) and (B) leading to CH3 + O -> HCHO + H (55 +/- 5)% -> CO + H-2 + H (45 +/- 5)%. The rate coefficients of the normal and deuterated methyl and ethyl radicals with atomic oxygen showed no isotope effect: k(CD3 + O)/k(CH3 + O) = 0.99 +/- 0.12, k(C2D5 + O)/k(C2H5 + O) = 1.01 +/- 0.07 (statistical error, 95% confidence level). The absolute rate coefficient of the reaction CH3 + O was derived with reference to the reaction C2H5 + O (k 1.04 x 10(14) cm(3) mol(-1) s(-1)) leading to k(CH3 + O) = (7.6 +/- 1.4) x 10(13) cm(3) mol(-1) s(-1)."],["dc.identifier.doi","10.1039/b419137d"],["dc.identifier.isi","000228634500014"],["dc.identifier.pmid","19787902"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20725"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Royal Soc Chemistry"],["dc.relation.issn","1463-9076"],["dc.title","Mechanism and rate of the reaction CH3+O- revisited"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","157"],["dc.bibliographiccitation.journal","Proceedings of the Combustion Institute"],["dc.bibliographiccitation.lastpage","164"],["dc.bibliographiccitation.volume","32"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Nacke, Frank"],["dc.contributor.author","Nothdurft, Joerg"],["dc.contributor.author","Olzmann, Matthias"],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:35:25Z"],["dc.date.available","2018-11-07T08:35:25Z"],["dc.date.issued","2009"],["dc.description.abstract","The primary product formation of the C(3)H(5) + O reaction in the gas phase has been studied at room temperature. Allyl radicals (C(3)H(5)) and O atoms were generated by laser flash photolysis at lambda = 193 nm of the precursors C(3)H(5)Cl, C(3)H(5)Br, C(6)H(10) (1,5-hexadiene), and SO(2), respectively. The educts and the products were detected by using quantitative FTIR spectroscopy. The combined product analysis of the experiments with the different precursors leads to the following relative branching fractions: C(3)H(5) + O -> C(3)H(4)O + H (47%), C(2)H(4) + H + CO (41'%), H(2)CO + C(2)H(2) + H (7%), CH(3)CCH + OH and CH(2)CCH(2) + OH (<5%). The rate of reaction has been studied relative to CH(3)OCH(2) + O and C(2)H(5) + O in the temperature range from 300 to 623 K. Here, the radicals were produced via the fast reactions of propene, dimethyl ether, and ethane, respectively, with atomic fluorine. Laser-induced multiphoton ionization combined with TOF mass spectrometry and molecular beam sampling from a flow reactor was used for the specific and sensitive detection of the C(3)H(5), C(2)H(5), and CH(3)COCH(2) radicals. The rate coefficient of the reaction C(3)H(5) + O was derived with reference to the reaction C(2)H(5) + O leading to k(C(3)H(5) + O) = (1.11 +/- 0.2) x 10(14) cm(3)/(mol s) in the temperature range 300-623 K. The C(3)H(5) + O rate and channel branching, when incorporated in a suitable detailed reaction mechanism, have a large influence on benzene and allyl concentration profiles in fuel-rich propene flames, on the propene flame speed, and on propene ignition delay times. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved."],["dc.identifier.doi","10.1016/j.proci.2008.06.220"],["dc.identifier.isi","000264756800013"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/18064"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Inc"],["dc.relation.issn","1540-7489"],["dc.title","The reaction of allyl radicals with oxygen atoms-rate coefficient and product branching"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1005"],["dc.bibliographiccitation.journal","Proceedings of the Combustion Institute"],["dc.bibliographiccitation.lastpage","1013"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Hack, W."],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Olzmann, M."],["dc.contributor.author","Viskolcz, B."],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:47:00Z"],["dc.date.available","2018-11-07T08:47:00Z"],["dc.date.issued","2005"],["dc.description.abstract","The reactions of the branched primary alkyl radicals iso-butyl and neo-pentyl radicals with atomic oxygen at room temperature and low pressure have been studied with respect to the mechanism of the multiple reaction channels and the rate coefficients. The primary products and the yield of the reaction channels have been determined by quantitative FTIR spectroscopy using laser flash photolysis for the production of the radicals and atoms (iSO-C4H10 + Cl, neo-C5H2 + Cl; Cl from the photolysis of CFCl3, O from SO2)- In an independent experimental arrangement of a conventional discharge flow reactor with molecular beam sampling, the hydrocarbon radicals were detected mass spectrometrically after specific laser induced multiphoton ionization, thus allowing the measurement of the rate coefficients with reference to the reaction C2H5 + O(k = 1.04 x 10(14) cm(3)/mol s). Both reactions show multichannel behaviour via the formation of a highly excited alkoxy radical followed by C-C and C-H bond cleavage and, in the case Of iso-C4H9 with a hydrogen atom in the 2-position, a direct abstraction to OH radicals: GRAPHICS The experimental results for the branching ratio for the C-C and C-H cleavage in the alkoxy intermediate are discussed in terms of statistical rate theory. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved."],["dc.identifier.doi","10.1016/j.proci.2004.08.072"],["dc.identifier.isi","000229944200107"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20836"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Inc"],["dc.publisher.place","New york"],["dc.relation.conference","30th International Symposium on Combustion"],["dc.relation.eventlocation","Univ Illinois Chicago, Chicago, IL"],["dc.relation.issn","1540-7489"],["dc.title","The reactions of the branched alkyl radicals iso-butyl and neo-pentyl with oxygen atoms - an experimental and theoretical study"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","3165"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry A"],["dc.bibliographiccitation.lastpage","3173"],["dc.bibliographiccitation.volume","110"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Nothdurft, J."],["dc.contributor.author","Olzmann, M."],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T10:06:56Z"],["dc.date.available","2018-11-07T10:06:56Z"],["dc.date.issued","2006"],["dc.description.abstract","The formation and the decomposition of chemically activated cyclopentoxy radicals from the C-C5H9 + O reaction have been studied in the gas phase at room temperature. Two different experimental arrangements have been used. Arrangement A consisted of a laser-flash photolysis set up combined with quantitative Fourier transform infrared spectroscopy and allowed the determination of the stable products at 4 mbar. The c-C5H9 radicals were produced via the reaction c-C5H10 + Cl with chlorine atoms from the photolysis of CFCl3; the O atoms were generated by photolysis of SO2. Arrangement B, a conventional discharge flow-reactor with molecular beam sampling, was used to determine the rate coefficient. Here, the hydrocarbon radicals (c-C5H9, C2H5, CH2OCH3) were produced via the reaction of atomic fluorine with c-C5H10, C2H6, and CH3OCH3, respectively, and detected by mass spectrometry after laser photoionization. For the c-C5H9 + 0 reaction, the relative contributions of intermediate formation (c-C5H9O ) and direct abstraction (C-C5H8 + OH) were found to be 68 +/- 5 and 32 +/- 4%, respectively. The decomposition products of the chemically activated intermediate could be identified, and the following relative branching fractions were obtained: C-C5H8O + H (31 +/- 2%), CH2CH(CH2)(2)CHO + H (40 +/- 5%), 2 C2H4 + H + CO (17 +/- 5%), and C3H4O + C2H4 + H (12 +/- 5%). Additionally, the product formation of the C-C5H8 + 0 reaction was studied, and the following relative yields were obtained (mol %): C2H4, 24%; C3H4O, 18%; c-C5H8O, 30%; c-C5H8O, 23%; 4-pentenal, 5%. The rate coefficient of the c-C5H9 + O reaction was determined relative to the reactions C2H5 + 0 and CH3OCH2 + O leading to k = (1.73 +/- 0.05) x 10(14) cm(3) mol(-1) s(-1). The experimental branching fractions are analyzed in terms of statistical rate theory with molecular and transition-state data from quantum chemical calculations, and high-pressure limiting Arrhenius parameters for the unimolecular decomposition reactions of C5H9O species are derived."],["dc.identifier.doi","10.1021/jp054578c"],["dc.identifier.isi","000235944000038"],["dc.identifier.pmid","16509640"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39191"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1089-5639"],["dc.title","Formation and decomposition of chemically activated cyclopentoxy radicals from the c-C5H9+O reaction"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]