An extended mechanism for chemical activation systems

Olzmann, Matthias; Gebhardt, J.; Scherzer, K.

doi:10.1002/kin.550230909

Cited by 18 publications

(15 citation statements)

References 30 publications

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“…Here, the symbol * indicates that the intermediate C is chemically activated, i.e., obeys a nonthermal energetic distribution, which is influenced by reactions (a)–(c) and collisions with the bath gas. For general aspects of chemical activation, the reader is referred to the monographs and for the influence of consecutive bimolecular steps to .…”

Section: Methodsmentioning

confidence: 99%

“…In case of nonthermal reactants A and B with normalized populations ñ A (ε) and ñ B (ε), respectively, the nascent distribution of C can be approximated by the shifted convolution

\begin{matrix} true \\ right f (E) = \int_{0}^{E - E_{0 (- normala)}} {\overset{n}{true}}_{normalA} (ɛ) {\overset{n}{true}}_{normalB} (E - E_{0 (- normala)} - ɛ) d ɛ \end{matrix}

with E ≥ E 0(–a) . Here, it is assumed that the reactive cross section of reaction (a) is independent of the internal energies of the reactants A and B, which is equivalent to the assumption that the rate of the reverse reaction (–a) can be described by (vibrational) phase space theory neglecting angular momentum restrictions (see discussions in ).…”

Section: Methodsmentioning

confidence: 99%

“…For general aspects of chemical activation, the reader is referred to the monographs [11][12][13] and for the influence of consecutive bimolecular steps to [17,[27][28][29][30].…”

Section: A 2bmentioning

confidence: 99%

See 2 more Smart Citations

Consecutive Chemical Activation Steps in the OH‐Initiated Atmospheric Degradation of Isoprene: An Analysis with Coupled Master Equations

Pfeifle

Olzmann

2014

Int J of Chemical Kinetics

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The influence of a two-step chemical activation on 1,5-H and 1,6-H shift reactions of hydroxyl-peroxy radicals formed in the atmospheric photooxidation of isoprene was investigated by means of a master equation analysis. To account for multiple chemical activation processes, three master equations were coupled. The general approach of this coupling is described, and consequences for steady-state regimes are examined. The specific calculations show that chemical activation has no substantial influence on the rate coefficients of the above-mentioned reactions under tropospheric conditions. However, it is demonstrated that high-pressure limits of the thermal rate coefficients instead of the falloff-corrected values have to be used for kinetic modeling. This is a consequence of the continuous population of the high-energy part of the isoprene-OH-O 2 adduct distribution by the forming reactions under steady-state conditions. The rate coefficients of the isomerization reactions at T = 298 K were calculated to be k 3a ∞ = 1.5 × 10 −3 s −1 (1,5-H-shift of the 1,2-isomer) and k 4a ∞ = 6.5 s −1 (1,6-H-shift of the (Z)-1,4-isomer). The calculated value of k 4a ∞ is three orders of magnitude larger than a recently reported experimentally observed rate coefficient for the hydrogen shift reactions of the hydroxyl-peroxy intermediates. It is shown that this discrepancy is in part due to the fact that the experiment does not distinguish between different structural isomers. A comparison of the experimentally determined isotope effect with the calculated value shows a reasonable agreement. C

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Section: Methodsmentioning

confidence: 99%

“…In case of nonthermal reactants A and B with normalized populations ñ A (ε) and ñ B (ε), respectively, the nascent distribution of C can be approximated by the shifted convolution

\begin{matrix} true \\ right f (E) = \int_{0}^{E - E_{0 (- normala)}} {\overset{n}{true}}_{normalA} (ɛ) {\overset{n}{true}}_{normalB} (E - E_{0 (- normala)} - ɛ) d ɛ \end{matrix}

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Consecutive Chemical Activation Steps in the OH‐Initiated Atmospheric Degradation of Isoprene: An Analysis with Coupled Master Equations

Pfeifle

Olzmann

2014

Int J of Chemical Kinetics

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“…Active parameters were also included to describe uncertainties in the product branching ratios due to model structural uncertainties in the treatment of reaction sequences proceeding through multiple chem-ically activated steps-creating potential for non-Boltzmann reactant distributions (e.g., [17,[78][79][80][81][82][83][84][85][86]). For the remaining reactions, Arrhenius parameters, ln(A), n, and E a , were used as the active parameters.…”

Section: Cl-initiated Low-temperature C 3 H 8 Oxidationmentioning

confidence: 99%

Harnessing the Combined Power of Theoretical and Experimental Data through Multiscale Informatics

Burke

2016

Int J of Chemical Kinetics

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Monumental, recent and rapidly continuing, improvements in the capabilities of ab initio theoretical kinetics calculations provides reason to believe that progress in the field of chemical kinetics can be accelerated through a corresponding evolution of the role of theory in kinetic modeling and its relationship with experiment. The present article reviews and provides additional demonstrations of the unique advantages that arise when theoretical and experimental data across multiple scales are considered on equal footing, including the relevant uncertainties of both, within a single mathematical framework. Namely, the multiscale informatics framework simultaneously integrates information from a wide variety of sources and scales: ab initio electronic structure calculations of molecular properties, rate constant determinations for individual reactions, and measured global observables of multireaction systems. The resulting model representation consists of a set of theoretical kinetics parameters (with constrained uncertainties) that are related through elementary kinetics models to rate constants (with propagated uncertainties) that in turn are related through physical models to global observables (with propagated uncertainties). An overview of the approach and typical implementation is provided along with a brief discussion of the major uncertainties (parametric and structural) in theoretical kinetics calculations, kinetic models for complex chemical mechanisms, and physical models for experiments. Higher levels of automation in all aspects, including closed‐loop autonomous mixed‐experimental‐and‐computational model improvement, are advocated for facilitating scalability of the approach to larger systems with reasonable human effort and computational cost. The unique advantages of combining theoretical and experimental data across multiple scales are illustrated through a series of examples. Previous results demonstrating the utility of simultaneous interpretation of theoretical and experimental data for assessing consistency in complex systems and for reliable, physics‐based extrapolation of limited data are briefly summarized. New results are presented to demonstrate the high predictive accuracy of multiscale informed models for both small (molecular properties) and large (global observables) scales. These new results provide examples where the optimization yields physically realistic parameter adjustments and where physical model uncertainties in experiments are larger than kinetic model uncertainties. New results are also presented to demonstrate the utility of the multiscale informatics approach for design of experiments and theoretical calculations, accounting for both theoretical and experimental existing knowledge as well as relevant parametric and structural uncertainties in interpreting potential new data. These new results provide examples where neglecting structural uncertainties in design of experiments results in failure to identify the most worthwhile experiment. Further progress in the c...

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“…Eine Auftrennung aller Elementarschritte dieses komplexen Geschehens allein an Hand der Reaktionsprodukte ist unmoglich. Uber theoretische Abschatzungen der Anteile verschiedener Aktivierungsschritte wird an anderer Stelle berichtet [36].…”

Section: -Methylheptanunclassified

Zur Reaktion von atomarem Wasserstoff mit 1‐Olefinen

Gebhardt

Scherzer

1991

J. Prakt. Chem.

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About the Reaction of Atomic Hydrogen with 1‐Olefines. Chemical activated reaction paths of the C2C8‐l‐olefines, initiated by atomic hydrogen, have been studied using an isothermal flow‐system (298 K, 130 Pa) with electrical discharge. In the reaction mixtures homologeous series of 1‐olefines and n‐alkanes were found which are identical with those of cycloolefine systems described previously [1, 2]. The reactions of the 1‐olefines are analysed and discussed in detail and compared to the cycloolefine reactions.

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An extended mechanism for chemical activation systems

Cited by 18 publications

References 30 publications

Consecutive Chemical Activation Steps in the OH‐Initiated Atmospheric Degradation of Isoprene: An Analysis with Coupled Master Equations

Consecutive Chemical Activation Steps in the OH‐Initiated Atmospheric Degradation of Isoprene: An Analysis with Coupled Master Equations

Harnessing the Combined Power of Theoretical and Experimental Data through Multiscale Informatics

Zur Reaktion von atomarem Wasserstoff mit 1‐Olefinen

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