Refractive index change and curvature in shock waves by angled beam refraction

Kiefer, J. H.; Manson, Anthony C.

doi:10.1063/1.1136779

Cited by 62 publications

(51 citation statements)

References 5 publications

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“…4 We have used either I-and C1-atom ARAS detection to determine rate constants in twelve of the fourteen studies. Kiefer and co-workers, who use the Laser Schlieren (LS) technique [27], have supplied additional data, and these collaborations have generally increased the T-range over which a particular reaction has been studied. In all cases, Arrhenius expressions, that do not include density effects, have been reported, and these are summarized in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…Troe and coworkers [28] have developed a methodology that is essentially a fit to the Rice-Ramsperger-Kassel-Marcus (RRKM) theory of unimolecular rate constants. This method has been applied to all of the present cases; however, we have also applied Gorin-model RRKM theory [ 16,27,29,30 ] and flexible transition state RRKM theory [16] to several of the cases. Regardless of which of the three methods is used, a transition state, including molecular parameters, must be identified using, at least, semiempirical and, sometimes, ab initio electronic structure theory.…”

Section: Resultsmentioning

confidence: 99%

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Thermal Decomposition Studies of Halogenated Organic Compounds

Michael¹,

Kumaran²

1998

Combustion Science and Technology

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Thermal Decomposition Studies of Halogenated Organic Compounds

Michael¹,

Kumaran²

1998

Combustion Science and Technology

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“…connected to a 10 ft driven section of 2.5 in. i.d., an arrangement whose details have been fully described [8]. Details of the LS diagnostics have also been given before [9].…”

Section: Methodsmentioning

confidence: 99%

“…Among other features the software now determines the (chemically) frozen shock parameters and also calculates the Blythe and Blackman corrections [10] used below in the analysis of vibrational relaxation. As before [8], velocities were set by interpolation of four intervals calculated from measured times centered about the LS beam. On the basis of extensive experience, the uncertainty in velocity is estimated as ±0.2%, corresponding to a temperature error of <±0.5%, here approx.…”

Section: Methodsmentioning

confidence: 99%

A shock tube, laser‐schlieren study of the pyrolysis of isobutene: Relaxation, incubation, and dissociation rates

Santhanam

Kiefer

Tranter

et al. 2003

Int J of Chemical Kinetics

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Dissociation, vibrational relaxation, and unimolecular incubation have all been observed in shock waves in isobutene with the laser-schlieren technique. Experiments covered a wide range of high-temperature conditions: 900-2300 K, and post-incident shock pressures from 7 to 400 torr in 2, 5, and 10% mixtures with krypton. The surprising observation is that of vibrational relaxation, well resolved over the full temperature range. The resolved process is completely exponential, with relaxation times in the range 20-120 ns atm. Relaxation and dissociation are clearly separated for T > 1850 K, with estimated incubation times near 200 ns atm. Incubation is essential for modeling of the very low-pressure decomposition. Modeling of gradients with a chain mechanism initiated by CH fission produces an excellent fit and accurate dissociation rates that show severe falloff. A restricted-rotor, Gorin-model RRKM analysis fits these rates quite well with the known bond-energy as barrier and E down = 680 cm −1 . The extrapolated k ∞ is log k ∞ (s −1 ) = 19.187-0.865 log T −87.337 (kcal/mol)/RT, in good agreement with previous work.

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“…This software now determines chemically frozen, but vibrationally equilibrated, ideal-shock parameters and also calculates the Blythe and Blackman corrections [40] used in the analysis of vibrational relaxation time. As before [37], velocities were set by interpolation of four intervals calculated from measured arrivals centered about the laser beam. On the basis of extensive experience, the uncertainty in velocity is estimated as ±0.2%, corresponding to a temperature error of less than ±0.5%, here amounting to the order of ±10 K.…”

Section: Experiments the Shock Tubementioning

confidence: 99%

Shock tube study of 1,3,5‐triazine dissociation and relaxation and relaxation of pyrazine

Kiefer

2010

Int J of Chemical Kinetics

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The three-body dissociation of 1,3,5-triazine (s-triazine, s-C 3 H 3 N 3 → 3HCN) has been observed in incident shock waves with the laser-schlieren technique. The experiments use 5% triazine/Kr and cover 1630-2350 K for 100-600 Torr. These experiments show dissociation rates with strong falloff and a slight but fully expected pressure dependence. The dissociation is without secondary reaction save for a possible, but rather unlikely, contribution from the isomerization HCN → HNC. Electronic structure calculations of the transitionstate properties (G3B3, HL1, E o = 84.6 kcal/mol) are used to construct a Rice-RamspergerKassel-Marcus (RRKM) model whose fit to the rate measurements suggests a E down of 1200 cm −1 . However, a seemingly better fit is achieved using the barrier of 81 kcal/mol proposed by Dyakov et al. (J. Phys. Chem. A 2007, 111, 9591-9599). With this barrier k ∞ (s −1 ) = 5.3 × 10 16 exp(−86.6(kcal/mol)/RT), and the fit now accepts the more routine E down = 126(T /298) 0.9 . It seems the dissociation most likely occurs by a direct, one-step, "triple" dissociation to 3HCN, although the present experiments cannot rule out a multistep process. Vibrational relaxation of the triazine was also examined in 5% and 20% mixtures with Kr over 770-1500 K for pressures between 6 and 14 Torr. Relaxation is very fast, with a slight inverse temperature dependence, P τ rising from 100 to 200 ns-atm over the full temperature range. Integrated gradients are in good accord with calculated total changes in density, indicating a single exponential relaxation. A separate investigation of relaxation in the related molecule pyrazine (500-1300 K, in 1% and 5% in Kr, between 13 and 66 Torr) is included. Again relaxation is rapid, but here the temperature dependence seems more normal, the relaxation times decreasing slightly with temperature. C

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Refractive index change and curvature in shock waves by angled beam refraction

Cited by 62 publications

References 5 publications

Thermal Decomposition Studies of Halogenated Organic Compounds

Thermal Decomposition Studies of Halogenated Organic Compounds

A shock tube, laser‐schlieren study of the pyrolysis of isobutene: Relaxation, incubation, and dissociation rates

Shock tube study of 1,3,5‐triazine dissociation and relaxation and relaxation of pyrazine

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