Horst Hippler - Academia.edu (original) (raw)
Papers by Horst Hippler
C-C and C-H bond splits of laser-excited aromatic molecules. 3. UV multiphoton excitation studies
The Journal of Physical Chemistry, 1990
Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation ... more Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation of cycloheptatriene, toluene, and ethylbenzene. The dependence on laser fluence and bath gas pressure is recorded. The results are interpreted in terms of a competition between the absorption of one or two photons, unimolecular reactions, and collisional deactivation of the parent molecules. The yields of the products CHâ and benzyl decrease at high laser fluences, probably because of secondary spontaneous fragmentations of these highly excited primary fragments.
The Journal of Physical Chemistry, 1986
The user has requested enhancement of the downloaded file. (9) Dillon, M. A,, private communicati... more The user has requested enhancement of the downloaded file. (9) Dillon, M. A,, private communication. The collisional energy transfer between excited SO2 and Ar has been simulated by classical trajectory calculations. The influences of the intramolecular and intermolecular potentials, of temperature, and of excitation of SO2 on vibrational and rotational energy transfer are demonstrated. Average energies transferred and collisional transition probabilities are reported.
Thermodynamic properties of benzyl radicals: enthalpy of formation from toluene, benzyl iodide, and dibenzyl dissociation equilibria
The Journal of Physical Chemistry, 1990
The temperature and pressure dependence of the reaction CH + H2if and only ifCH3if and only ifCH2 + H
Chem Phys, 1997
Thermal rate constants of the reaction of CH(2Π) with H2 have been measured at pressures between ... more Thermal rate constants of the reaction of CH(2Π) with H2 have been measured at pressures between 1 and 160 bar and temperatures between 185 and 800 K. CH radicals have been generated using multiphoton laser flash photolysis of CHBr3 at 248 nm and detected by saturated laser-induced fluorescence near 430 nm. At low pressures the reaction leads to CH2(3B)and H, while at high pressures CH3 radicals are produced. S-shaped transition curves have been constructed to describe the pressure dependence of the rate constant. The high-pressure limiting rate constant for the recombination to CH3 has been evaluated to be k1,∞=2.0×10-10(T/300 K)0,15 cm3molecule-1 s-1. Using experimental low-pressure data from the literature, the rate constant for the second channel could be separated and has been analyzed in terms of SACM theory. A simple kinetic model has been applied to describe the overall rate constant k1 in an extended temperature and pressure range. Related rate constants for the reaction of CH2(3B) with H and the unimolecular two-channel dissociation of CH3 have also been analyzed.
C-C and C-H bond splits of laser-excited aromatic molecules. 1. Specific and thermally averaged rate constants
The Journal of Physical Chemistry, 1990
Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation ... more Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation of cycloheptatriene, toluene, and ethylbenzene. The dependence on laser fluence and bath gas pressure is recorded. The results are interpreted in terms of a competition between the absorption of one or two photons, unimolecular reactions, and collisional deactivation of the parent molecules. The yields of the products CHâ and benzyl decrease at high laser fluences, probably because of secondary spontaneous fragmentations of these highly excited primary fragments.
The thermal unimolecular decomposition of HCO: effects of state specific rate constants on the thermal rate constantElectronic supplementary information (ESI) available: Experimental data and conditions. See http://www.rsc.org/suppdata/cp/b4/b402139h/
Pccp Physical Chemistry Chemical Physics, Jul 9, 2004
Isomerization and Collisional Deactivation of Highly Vibrationally Excited Azulene Molecules After UV Excitation at 248 and 193 nm
The Journal of Physical Chemistry, 1991
... T. J.; Flynn, b. W. J. Chrm. ... 0 5 IO 15 20 t Ips Figure 1. Absorption-time profile of coll... more ... T. J.; Flynn, b. W. J. Chrm. ... 0 5 IO 15 20 t Ips Figure 1. Absorption-time profile of collision-free unimolecular isom-erization of azulene to naphthalene in the electronic ground state (laser excitation at 193 nm, analysis wavelength 290 nm, f(azulene) = 5 pbar; superposition of ...
Reaction of OH + NO 2 : High Pressure Experiments and Falloff Analysis †
The Journal of Physical Chemistry A, 2006
High pressure experiments on the OH + NO2 reaction are presented for 3 different temperatures. At... more High pressure experiments on the OH + NO2 reaction are presented for 3 different temperatures. At 300 K, experiments in He (p = 2-500 bar) as well as in Ar (p = 2-4 bar) were performed. The rate constants obtained in Ar agree well with values which have been reported earlier by our group (Forster, R.; Frost, M.; Fulle, D.; Hamann, H. F.; Hippler, H.; Schlepegrell, A.; Troe, J. J. Chem. Phys. 1995, 103, 2949. Fulle, D.; Hamann, H. F.; Hippler, H.; Troe, J. J. Chem. Phys. 1998, 108, 5391). In contrast, the rate coefficients determined in He were found to be 15-25% lower than the values given in our earlier publications. Additionally, results for He as bath gas at elevated temperatures (T = 400 K, p = 3-150 bar; T = 600 K, p = 3-150 bar) are reported. The results obtained at elevated pressures are found to be in good agreement with existing literature data. The observed falloff behavior is analyzed in terms of the Troe formalism taking into account two reaction channels: one yielding HNO3 and one yielding HOONO. It is found that the extracted parameters are in agreement with rate constants for vibrational relaxation and isotopic scrambling as well as with experimentally determined branching ratios. Based on our analysis we determine falloff parameters to calculate the rate constant for atmospheric conditions.
Proceedings of the Combustion Institute, 2002
The thermal decomposition of 2-, 3-, and 4-methylbenzyl radicals was studied behind reflected sho... more The thermal decomposition of 2-, 3-, and 4-methylbenzyl radicals was studied behind reflected shock waves. ␣-Bromoortho (meta-and para-)-xylenes were used as precursors for a series of experiments with temperatures ranging from 1150 to 1600 K and pressures between 1.5 and 4 bar. Mixtures of 1-5.5 ppm of the precursor diluted in argon were used for the investigations. Initiated by the fast thermal dissociation of the precursor
Competition between alkyl radical addition to carbonyl bonds and H-atom abstraction reactions
Physical Chemistry Chemical Physics, 2002
Reaction of OH + NO2 + M: Kinetic evidence of isomer formation
Physical Chemistry Chemical Physics, 2002
A detailed experimental and theoretical study on the decomposition of methoxy radicals
Physical Chemistry Chemical Physics, 2001
Laser powered homogeneous pyrolysis of butane initiated by methyl radicals in a quasi-wall-free reactor at 750–1000 K
Physical Chemistry Chemical Physics, 2000
Laser powered homogeneous pyrolysis of ethyne, propyne, and propadiene initiated by methyl radicals: formation and degradation of hydrocarbons at 800–950 K
Physical Chemistry Chemical Physics, 2002
Reply to the ?Comment on ?The thermal unimolecular decomposition of HCO: effects of state specific rate constants on the thermal rate constant??? by L. N. Krasnoperov, Phys. Chem. Chem. Phys., 2005, 7, DOI: 10.1039/b418813f
Physical Chemistry Chemical Physics, 2005
The high-pressure range of the reaction of CH(2Π) with N2
The Journal of Chemical Physics, 1996
Flash photolysis study of the recombination of chlorine atoms in the presence of various inert gases and NO
International Journal of Chemical Kinetics, 1976
Reactions of methyl radicals with isobutane at temperatures between 800 and 950 kelvin
International Journal of Chemical Kinetics, 2001
... at Temperatures Between 800 and 950 Kelvin ELKE GOOS,1 HORST HIPPLER,1 KARLHEINZ HOYERMANN,2 ... more ... at Temperatures Between 800 and 950 Kelvin ELKE GOOS,1 HORST HIPPLER,1 KARLHEINZ HOYERMANN,2 BETTINA J ¨URGES2 ... (3) Applying GCMS analysis allows the identifi-cation and quantification of the products, espe-cially of the different isomers. ...
Reactions of methyl radicals with propene at temperatures between 750 and 1000 K
Faraday Discussions, 2001
The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range... more The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range 750-1000 K and at a pressure of 0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational-translational (V-T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: a stationary heat balance, optical absorption, pressure rise, and the temperature dependence of the rate of an isomerization reaction. Methyl radicals were produced via the fast thermal dissociation of di-tert-butyl-peroxide and the products were analysed using GC-MS. The main products of the overall reaction of the model system propene and methyl (C3H6 + CH3) were isopentane (iso-C5H12) and but-1-ene (1-C4H8), whereas allene (C3H4), trans-but-2-ene (trans-2-C4H8) and cis-but-2-ene (cis-2-C4H8) were minor components, all showing a strong dependence on temperature. The product distribution and the temperature dependence were analysed by a kinetic model of 61 species and 166 reactions developed for the high-temperature oxidation of butane and the low-temperature oxidation of n-pentane and isopentane. It was necessary to include a few missing reactions and to adjust some rate constants to make the modeling agree with the experimental investigations. This extended mechanism has to be evaluated further in forthcoming experiments.
The Journal of Physical Chemistry, 1985
C-C and C-H bond splits of laser-excited aromatic molecules. 3. UV multiphoton excitation studies
The Journal of Physical Chemistry, 1990
Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation ... more Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation of cycloheptatriene, toluene, and ethylbenzene. The dependence on laser fluence and bath gas pressure is recorded. The results are interpreted in terms of a competition between the absorption of one or two photons, unimolecular reactions, and collisional deactivation of the parent molecules. The yields of the products CHâ and benzyl decrease at high laser fluences, probably because of secondary spontaneous fragmentations of these highly excited primary fragments.
The Journal of Physical Chemistry, 1986
The user has requested enhancement of the downloaded file. (9) Dillon, M. A,, private communicati... more The user has requested enhancement of the downloaded file. (9) Dillon, M. A,, private communication. The collisional energy transfer between excited SO2 and Ar has been simulated by classical trajectory calculations. The influences of the intramolecular and intermolecular potentials, of temperature, and of excitation of SO2 on vibrational and rotational energy transfer are demonstrated. Average energies transferred and collisional transition probabilities are reported.
Thermodynamic properties of benzyl radicals: enthalpy of formation from toluene, benzyl iodide, and dibenzyl dissociation equilibria
The Journal of Physical Chemistry, 1990
The temperature and pressure dependence of the reaction CH + H2if and only ifCH3if and only ifCH2 + H
Chem Phys, 1997
Thermal rate constants of the reaction of CH(2Π) with H2 have been measured at pressures between ... more Thermal rate constants of the reaction of CH(2Π) with H2 have been measured at pressures between 1 and 160 bar and temperatures between 185 and 800 K. CH radicals have been generated using multiphoton laser flash photolysis of CHBr3 at 248 nm and detected by saturated laser-induced fluorescence near 430 nm. At low pressures the reaction leads to CH2(3B)and H, while at high pressures CH3 radicals are produced. S-shaped transition curves have been constructed to describe the pressure dependence of the rate constant. The high-pressure limiting rate constant for the recombination to CH3 has been evaluated to be k1,∞=2.0×10-10(T/300 K)0,15 cm3molecule-1 s-1. Using experimental low-pressure data from the literature, the rate constant for the second channel could be separated and has been analyzed in terms of SACM theory. A simple kinetic model has been applied to describe the overall rate constant k1 in an extended temperature and pressure range. Related rate constants for the reaction of CH2(3B) with H and the unimolecular two-channel dissociation of CH3 have also been analyzed.
C-C and C-H bond splits of laser-excited aromatic molecules. 1. Specific and thermally averaged rate constants
The Journal of Physical Chemistry, 1990
Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation ... more Parent disappearance and fragment formation yields are measured in the UV multiphoton excitation of cycloheptatriene, toluene, and ethylbenzene. The dependence on laser fluence and bath gas pressure is recorded. The results are interpreted in terms of a competition between the absorption of one or two photons, unimolecular reactions, and collisional deactivation of the parent molecules. The yields of the products CHâ and benzyl decrease at high laser fluences, probably because of secondary spontaneous fragmentations of these highly excited primary fragments.
The thermal unimolecular decomposition of HCO: effects of state specific rate constants on the thermal rate constantElectronic supplementary information (ESI) available: Experimental data and conditions. See http://www.rsc.org/suppdata/cp/b4/b402139h/
Pccp Physical Chemistry Chemical Physics, Jul 9, 2004
Isomerization and Collisional Deactivation of Highly Vibrationally Excited Azulene Molecules After UV Excitation at 248 and 193 nm
The Journal of Physical Chemistry, 1991
... T. J.; Flynn, b. W. J. Chrm. ... 0 5 IO 15 20 t Ips Figure 1. Absorption-time profile of coll... more ... T. J.; Flynn, b. W. J. Chrm. ... 0 5 IO 15 20 t Ips Figure 1. Absorption-time profile of collision-free unimolecular isom-erization of azulene to naphthalene in the electronic ground state (laser excitation at 193 nm, analysis wavelength 290 nm, f(azulene) = 5 pbar; superposition of ...
Reaction of OH + NO 2 : High Pressure Experiments and Falloff Analysis †
The Journal of Physical Chemistry A, 2006
High pressure experiments on the OH + NO2 reaction are presented for 3 different temperatures. At... more High pressure experiments on the OH + NO2 reaction are presented for 3 different temperatures. At 300 K, experiments in He (p = 2-500 bar) as well as in Ar (p = 2-4 bar) were performed. The rate constants obtained in Ar agree well with values which have been reported earlier by our group (Forster, R.; Frost, M.; Fulle, D.; Hamann, H. F.; Hippler, H.; Schlepegrell, A.; Troe, J. J. Chem. Phys. 1995, 103, 2949. Fulle, D.; Hamann, H. F.; Hippler, H.; Troe, J. J. Chem. Phys. 1998, 108, 5391). In contrast, the rate coefficients determined in He were found to be 15-25% lower than the values given in our earlier publications. Additionally, results for He as bath gas at elevated temperatures (T = 400 K, p = 3-150 bar; T = 600 K, p = 3-150 bar) are reported. The results obtained at elevated pressures are found to be in good agreement with existing literature data. The observed falloff behavior is analyzed in terms of the Troe formalism taking into account two reaction channels: one yielding HNO3 and one yielding HOONO. It is found that the extracted parameters are in agreement with rate constants for vibrational relaxation and isotopic scrambling as well as with experimentally determined branching ratios. Based on our analysis we determine falloff parameters to calculate the rate constant for atmospheric conditions.
Proceedings of the Combustion Institute, 2002
The thermal decomposition of 2-, 3-, and 4-methylbenzyl radicals was studied behind reflected sho... more The thermal decomposition of 2-, 3-, and 4-methylbenzyl radicals was studied behind reflected shock waves. ␣-Bromoortho (meta-and para-)-xylenes were used as precursors for a series of experiments with temperatures ranging from 1150 to 1600 K and pressures between 1.5 and 4 bar. Mixtures of 1-5.5 ppm of the precursor diluted in argon were used for the investigations. Initiated by the fast thermal dissociation of the precursor
Competition between alkyl radical addition to carbonyl bonds and H-atom abstraction reactions
Physical Chemistry Chemical Physics, 2002
Reaction of OH + NO2 + M: Kinetic evidence of isomer formation
Physical Chemistry Chemical Physics, 2002
A detailed experimental and theoretical study on the decomposition of methoxy radicals
Physical Chemistry Chemical Physics, 2001
Laser powered homogeneous pyrolysis of butane initiated by methyl radicals in a quasi-wall-free reactor at 750–1000 K
Physical Chemistry Chemical Physics, 2000
Laser powered homogeneous pyrolysis of ethyne, propyne, and propadiene initiated by methyl radicals: formation and degradation of hydrocarbons at 800–950 K
Physical Chemistry Chemical Physics, 2002
Reply to the ?Comment on ?The thermal unimolecular decomposition of HCO: effects of state specific rate constants on the thermal rate constant??? by L. N. Krasnoperov, Phys. Chem. Chem. Phys., 2005, 7, DOI: 10.1039/b418813f
Physical Chemistry Chemical Physics, 2005
The high-pressure range of the reaction of CH(2Π) with N2
The Journal of Chemical Physics, 1996
Flash photolysis study of the recombination of chlorine atoms in the presence of various inert gases and NO
International Journal of Chemical Kinetics, 1976
Reactions of methyl radicals with isobutane at temperatures between 800 and 950 kelvin
International Journal of Chemical Kinetics, 2001
... at Temperatures Between 800 and 950 Kelvin ELKE GOOS,1 HORST HIPPLER,1 KARLHEINZ HOYERMANN,2 ... more ... at Temperatures Between 800 and 950 Kelvin ELKE GOOS,1 HORST HIPPLER,1 KARLHEINZ HOYERMANN,2 BETTINA J ¨URGES2 ... (3) Applying GCMS analysis allows the identifi-cation and quantification of the products, espe-cially of the different isomers. ...
Reactions of methyl radicals with propene at temperatures between 750 and 1000 K
Faraday Discussions, 2001
The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range... more The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range 750-1000 K and at a pressure of 0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational-translational (V-T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: a stationary heat balance, optical absorption, pressure rise, and the temperature dependence of the rate of an isomerization reaction. Methyl radicals were produced via the fast thermal dissociation of di-tert-butyl-peroxide and the products were analysed using GC-MS. The main products of the overall reaction of the model system propene and methyl (C3H6 + CH3) were isopentane (iso-C5H12) and but-1-ene (1-C4H8), whereas allene (C3H4), trans-but-2-ene (trans-2-C4H8) and cis-but-2-ene (cis-2-C4H8) were minor components, all showing a strong dependence on temperature. The product distribution and the temperature dependence were analysed by a kinetic model of 61 species and 166 reactions developed for the high-temperature oxidation of butane and the low-temperature oxidation of n-pentane and isopentane. It was necessary to include a few missing reactions and to adjust some rate constants to make the modeling agree with the experimental investigations. This extended mechanism has to be evaluated further in forthcoming experiments.
The Journal of Physical Chemistry, 1985