Reaction of hot and thermal hydrogen atoms with hydrogen bromide and bromine

Fass, Richard A.

doi:10.1021/j100700a003

Cited by 17 publications

(3 citation statements)

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“…-HBr + Br reactions and the reaction ratio for these two reactions have also been determined. 24 Theoretical work on the H2Br system dates back to the 1930s, when Eyring and P~l a n y i ,~~ in their historic paper, presented the first analytic potential energy surface for this system. Since then several different potential energy surfaces have been developed for this system, and a number of different theoretical methods have been applied in the study of the dynamics of this chemical system.…”

Section: Introductionmentioning

confidence: 99%

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

et al. 1995

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We have carried out multireference configuration interaction calculations with a large basis set for the H2Br system at 104 geometriel preselected for convenient use in fitting an analytic potential energy surface for the reactions H + HBr -H2Br and H + H'Br -H' + HBr. The external part of the correlation energy is scaled (SEC method) to yield a 101 geometry data set which is fitted using the extended London-Eyring-PolanyiSat0 method with bond-distance-and internal-angle-dependent Sat0 parameters plus a three-center term localized at the collinear H-Br-H saddle point. The unweighted root-mean-square error for 88 points corresponding to collinear and bent H-H-Br geometries and collinear H-Br-H geometries is 0.55 kcaYmo1, with larger deviations for bent H-Br-H geometries. Rate constants were calculated by combining the new analytic potential energy surface with improved canonical variational transition state theory and the least-action semiclassical tunneling approximation. For the abstraction reaction, H + HBr -H2 + Br, and four deuterium and muonium isotopic analogs, agreement with experiment is very good; however, it would probably be better if the 1.9 kcaYmo1 classical barrier height on the analytic potential energy surface were lowered by 0.15-0.6 kcaYmo1. In contrast to the previous interpretation of the experimental results for Mu -t HBr, our calculations show that the Mu + HBr reaction is dominated by tunneling at all temperatures for which it was studied experimentally, up to 479 K. Tunneling is also found to be important for H + HBr and H + DBr, increasing the predicted rates at 300 K by factors of 2.6 and 1.8, respectively, whereas the same factor is only 1.4 for both D + HBr and D + DBr. Agreement with experiment is much less satisfactory for the exchange reactions D + HBr z z DBr + H; the present barrier height of 12 kcaYmol would have to be lowered about 7-9 kcaYmol to improve this situation. The assumption that high-frequency vibrations remain adiabatic prior to the region of large reaction path curvature predicts that vibrational excitation increases the reaction rate by factors of 1600-19 000 at 600 K, in qualitative agreement with the experimental factors of 3100-37 000.

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Section: Introductionmentioning

confidence: 99%

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

et al. 1995

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“…Our value for kFBr is almost four times larger than theirs, our kFBr is about one third as large as theirs, and our k3 is the same as or one half as large as theirs. (Westberg and Greene [38] have since reexamined their conclusions in the light of Fass's work [27]. They chose a rate coefficient for kL3 nearly identical to the value of rate N, and found they could fit their experimental results with a value for However, their results are still not completely consistent with ours as they found it necessary to make kFBr /ki' = 3.)…”

Section: Results and Conclusionmentioning

confidence: 89%

“…Actually, Britton and Cole did not assume the value of k-3/k2 to be known, but varied it in order to obtain the most consistent set of rate coefficients. At 1300"K, they found the ratio to vary The two most reliable determinations appear to be the recent ones of Fass [27] and Vidal [28]. Fass studied the competition between HBr and Brz for H atoms produced by HBr photolysis in the presence of Brz at 300-523°K.…”

Section: A Exchange Reactionsmentioning

confidence: 99%

Further Studies on the Dissociation of HBr Behind Shock Waves

Cohen¹,

Giedt²,

Jacobs³

1972

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APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED LABORATORY OPERATIONSThe Laboratory Operations of The Aerospace Corporation is conducting experimental and theoretical investigations necessary for the evaluation and application of scientific advances to new military concepts and systems. 'Versatility and flexibility have been developed to a high degree by the laboratory personnel in dealing with the many problems encountered in the nation's rapidly developing space and missile systems. Expertise in the latest scientific developinents is vital to the accomplishment of tasks related to these problems. The laboratories that contribute to this research are:Aerodynamics and Propulsion Research Laboratory: Launch and reentry aerodynamics, heat transfer, reentry physics, propulsion, high -temperature chemistry and chemical kinetics, structural mechanics, flight dynamics, atmospheric pollution, and high-power gas lasers.Electronics Research Laboratory: Generation, transmission, detection, and processing of electromagnetic radiation in the terrestrial and space environments, with emphasis on the millimeter-wave, infrared, and visible portions of the spectrum; design and fabrication of antennas, complex optical systems. and photolihhographic" solid-state devices; test and development of practical superconducting detectors and laser eevices and technology, including highpower lasers, atmospheric polli tion, and biomedical prou*.ems.Materials Sciences Labo aton, Development of new materials; metal inatrix composites and new foy ms of carbon; test and evaluation of graphite and ceramics in reentry; spacecraft materials and components in radiation and high -vacuum environments; application of fracture mechanics to stress corrosion and fatigue-induced fractures in structural metals; effect of nature of material surfaces on lubrication, photosensitiztion, and catalytic reactions; and development of prosthesis devices. Plasma Research Laboratory: Reentry physics and nuclear weapons effects; the interaction of antennas with reentry plasm~a sheaths; experimentation with thermonuclear plasmas; the generation and propagation of plasma waves in the magnetosphere; chemical reactions of vibralionally excited species in rocket plumes; and high-precision laser ranging. Space Physics Laboratory: Aeronomy; density and composition of the atmosphere at all altitudes; atmospheric reactions and atmospheric optics; pollution of the environment; the sun, earth's resources; meteorological measurements; radiation belts and cosmic rays. and the effects of nuclear explosvns, magnetic storms, and solar radiation on the atmosphere, Previously reported shock tube studies of the dissociation of HBr i,. nhe temperature range of 2100-4200°K have been extended to lower temperatures (1450-2300°K) in pure HBr. The course of reaction was followed by monitoring the radiative recombination emission in the visible spectrum from Br atoms. The results imply that, in the lower range of temperatures, the activation energy of dissociation can be approximated by th...

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Rate measurements for the reactions H + I₂→ HI + I and H + HI → H₂+ I by Lyman‐α‐fluorescence

Lorenz

Wagner

Zellner

1979

Ber Bunsenges Phys Chem

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Rate constants for the reactions of hydrogen atoms with I2(k1) and HI(k2) have been determined in a discharge flow system using the detection of H‐atoms by Lyman‐α resonance fluorescence. Temperature dependent measurements in the range 250–420 K for H + I2 show an extremely weak variation with temperature k1,(H + I2) = (6.6 ± 3) 10−10 exp(‐20 K/T) cm3/molecule · s. which is equally well represented by the temperature independent expression k1, = (6 ± 2.5) 10−10 cm3/molecule · s. — From rate measurements for H + HI in the range 250–370 K the Arrhenius expression k2(H + HI) = (7.4 ± 2.0) 10−11 exp(‐290 K/T) cm3/molecule · s is obtained.

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Reaction of hot and thermal hydrogen atoms with hydrogen bromide and bromine

Cited by 17 publications

References 1 publication

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

Further Studies on the Dissociation of HBr Behind Shock Waves

Rate measurements for the reactions H + I₂→ HI + I and H + HI → H₂+ I by Lyman‐α‐fluorescence

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Reaction of hot and thermal hydrogen atoms with hydrogen bromide and bromine

Cited by 17 publications

References 1 publication

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

A New Potential Energy Surface for H2Br and Its Use To Calculate Branching Ratios and Kinetic Isotope Effects for the H + HBr Reaction

Further Studies on the Dissociation of HBr Behind Shock Waves

Rate measurements for the reactions H + I2→ HI + I and H + HI → H2+ I by Lyman‐α‐fluorescence

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Rate measurements for the reactions H + I₂→ HI + I and H + HI → H₂+ I by Lyman‐α‐fluorescence