The kinetics of the reaction F + H2 ? HF + H. A critical review of literature data

Persky, Avigdor; Kornweitz, Haya

doi:10.1002/(sici)1097-4601(1997)29:1<67::aid-kin8>3.0.co;2-j

Cited by 39 publications

(28 citation statements)

References 21 publications

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“…3, the long range entrance channel region was merged to the SW PES in a way so to leave unmodified the energy of the transition state. A near perfect agreement with measured rate constants 21 was obtained for the F + H 2 reaction at temperatures between 200 and 335 K showing the key role of our corrections especially in the cold condition regime. Spin-orbit effects are expected to be even more important for the F + HD variant.…”

Section: Introductionsupporting

confidence: 76%

Exact quantum calculations of the kinetic isotope effect: Cross sections and rate constants for the F+HD reaction and role of tunneling

Fazio

Aquilanti

Cavalli

et al. 2006

The Journal of Chemical Physics

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In this paper we present integral cross sections (in the 5-220 meV collision energy range) and rate constants (in the 100-300 K range of temperature) for the F+HD reaction leading to HF+D and DF+H. The exact quantum reactive scattering calculations were carried out using the hyperquantization algorithm on an improved potential energy surface which incorporates the effects of open shell and fine structure of the fluorine atom in the entrance channel. The results reproduce satisfactorily molecular beam scattering experiments as well as chemical kinetics data for both the HF and DF channels. In particular, the agreement of the rate coefficients and the vibrational branching ratios with experimental measurements is improved with respect to previous studies. At thermal and subthermal energies, the rates are greatly influenced by tunneling through the reaction barrier. Therefore exchange of deuterium is shown to be penalized with respect to exchange of hydrogen, and the isotopic branching exhibits a strong dependence on translational energy. Also, it is found that rotational excitation of the reactant HD molecule enhances the production of HF and decreases the reactivity at the D end, obtaining insight on the reaction stereodynamics.

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Section: Introductionsupporting

confidence: 76%

Exact quantum calculations of the kinetic isotope effect: Cross sections and rate constants for the F+HD reaction and role of tunneling

Fazio

Aquilanti

Cavalli

et al. 2006

The Journal of Chemical Physics

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“…that we take to be the ratio of the numerically exact rate constant k , obtained from rigorous quantum scattering calculations, to the tunneling corrected rate constants k Q , calculated from Equation (11) using the Arrhenius parameters A and V * reported in Persky and Kornweitz (1997). The values of T c have been obtained by imposing the limit for T = 0 of Equation (11) equal to Equation (10), namely:…”

Section: Resultsmentioning

confidence: 99%

Quantum Dynamics and Kinetics of the F + H2 and F + D2 Reactions at Low and Ultra-Low Temperatures

2019

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Integral cross sections and rate constants for the prototypical chemical reactions of the fluorine atom with molecular hydrogen and deuterium have been calculated over a wide interval of collision energy and temperature ranging from the sub-thermal (50 K) down to the ultra-cold regimes (0.5 mK). Rigorous close coupling time-independent quantum reactive scattering calculations have been carried out on two potential energy surfaces, differing only at long-range in the reactants' channel. The results show that tunnel, resonance and virtual state effects enhance under-barrier reactivity giving rise to pronounced deviations from the Arrhenius law as temperature is lowered. Within the ultra-cold domain (below 1 mK), the reactivity is governed by virtual state effects and by tunneling through the reaction barrier; in the cold regime (1 mK–1 K), the shape resonances in the entrance channel of the potential energy surface make the quantum tunneling contribution larger so enhancing cross sections and rate constants by about one order of magnitude; at higher temperatures (above 10 K), the tunneling pathway enhanced by the constructive interference between two Feshbach resonances trapped in the reaction exit channel competes with the thermally activated mechanism, as the energy gets closer to the reaction barrier height. The results show that at low temperatures cross sections and rate constants are extremely sensitive to small changes in the long-range intermolecular interaction in the entrance channel of the potential energy surface, as well as to isotopic substitution.

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“…32 Corresponding high level ab initio calculations and simulations 33 have achieved very good agreement with experiment. The vibrational distribution remains unchanged from the 1982 Cohen and Bott report, 3 34 Unfortunately, the limited temperature range of the Persky expression is problematic for HF laser modeling, since the laser typically operates at substantially higher temperatures. To date, there has been only one experiment that has measured k(FϩH 2 ) above 376 K. Heidner and co-workers 38 monitored the time-resolved infrared emission of product HF following multiphoton dissociation of SF 6 Some CFD codes 5 include F atom reactions with vibrationally excited H 2 even though this process was not included in the original Cohen and Bott compilations.…”

Section: Fϩhmentioning

confidence: 99%

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

Manke

Hager

2001

Journal of Physical and Chemical Reference Data

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An abbreviated review of rate coefficients relevant to HFI laser kinetics modeling is presented. The literature has been surveyed from the last published review in 1983 to the present. Updated HF Einstein emission coefficients are tabulated. This brief summary of a more detailed review addresses rate coefficients relevant to HIF generation, reactive quenching, self-relaxation, and vibrational relaxation by a selection of atoms and molecules. In addition, a review of recent experiments and theoretical calculations relevant to the role of rotational non-equilibrium in HF lasers is presented. A list of recommended temperature dependent expressions for critical reaction rate coefficients is given. INTRODUCTIONSince its invention in the mid-1960's, the HF laser system has been extensively studied and developed to the point where megawatt-class devices can be built. In fact, most of the research in the recent past has focused on large-scale laser technology demonstrations. Despite the enormous effort expended to accomplish this, a complete understanding of all facets of HF laser performance is still evolving and is not complete. For example, research continues into the role of reagent mixing and heat transfer between the fluids and the construction material of the device. Combustor instabilities and other complex, transient, fluid dynamical features also impede our understanding of the laser's performance.The only way to achieve insight into the details of the HF laser is to employ computational fluid dynamical (CFD) codes that can integrate the complex fluid properties with the myriad chemical reactions that occur in the laser cavity. Unfortunately (although perhaps not surprisingly considering the complexity of the problem), CFD codes have had limited success at accurately modeling real HIF laser systems. As a result, both the laser performance data and the reaction rate constants used to baseline the models have come under increased scrutiny in recent years. This scrutiny has uncovered serious questions about the kinetics package that have yet to be answered conclusively. These questions include the importance of rotational nonequilibrium, the magnitude of various quenching processes, the role of three body and heterogeneous fluorine atom recombination, and other fundamental properties such as Einstein coefficients.The main topics of this report (in order of their presentation) are Einstein coefficients and relevant kinetic measurements. It is not within the scope of this document to discuss fluid dynamics issues, such as recently developed 3 dimensional computational fluid dynamics (CFD) codes or new algorithms to model mixing or optical resonators.

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The kinetics of the reaction F + H2 ? HF + H. A critical review of literature data

Cited by 39 publications

References 21 publications

Exact quantum calculations of the kinetic isotope effect: Cross sections and rate constants for the F+HD reaction and role of tunneling

Exact quantum calculations of the kinetic isotope effect: Cross sections and rate constants for the F+HD reaction and role of tunneling

Quantum Dynamics and Kinetics of the F + H2 and F + D2 Reactions at Low and Ultra-Low Temperatures

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

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