Erratum: “Relative formation rates of O350 and O352 in O–16O18 mixtures” [J. Chem. Phys. <b>111</b>, 7179 (1999)]

Janssen, Christof; Guenther, Juergen; Krankowsky, D.; Mauersberger, K.

doi:10.1063/1.481761

Cited by 24 publications

(32 citation statements)

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“…We note that the recent experiments on the rate constants of the individual channels 27 ͑symmetric vs asymmetric products͒ validate the present assumption that the addition is primarily ''end on,'' with very little contribution, if any, to the products resulting from insertion of an oxygen atom into the O 2 bond. ͑The current experimental results indicate that insertion into the bond is less than Ͻ1% of the end-on attack.͒ As noted previously, the PST transition state utilized in these calculations is quite loose, and cannot correctly account for the well known [56][57][58][59][60][61][62][63][64][65][66][67][68] tightening of the transition state which typically occurs at higher energies, and thus at higher temperatures.…”

Section: Discussionmentioning

confidence: 57%

“…15%͒ non-Rice-Ramsperger-KasselMarcus ͑RRKM͒ effect gave rise to a dramatic effect, the so-called mass-independent isotope effect, in ozone formation. Recently, experiments on specific elementary reaction steps, [25][26][27][28] in contrast with scrambled systems, showed dramatic mass-dependent effects. This dichotomy between the behavior of individual recombination steps and of scrambled systems is treated in the present paper, using the formalism given in paper I.…”

Section: Introductionmentioning

confidence: 99%

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An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

Hathorn

Marcus

2000

The Journal of Chemical Physics

104

112

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A theory is described for the variation in the rate constants for formation of different ozone isotopomers from oxygen atoms and molecules at low pressures. The theory is implemented using a simplified description which treats the transition state as loose. The two principal features of the theory are a phase space partitioning of the transition states of the two exit channels after formation of the energetic molecule and a small ͑ca. 15%͒ decrease in the effective density of states, ͓a ''non-Rice-Ramsperger-Kassel-Marcus ͑RRKM͒ effect''͔, for the symmetric ozone isotopomers ͓B. C. Hathorn and R. A. Marcus, J. Chem. Phys. 111, 4087 ͑1999͔͒. This decrease is in addition to the usual statistical factor of 2 for symmetric molecules. Experimentally, the scrambled systems show a ''mass-independent'' effect for the enrichments ␦ ͑for trace͒ and E ͑for heavily͒ enriched systems, but the ratios of the individual isotopomeric rate constants for unscrambled systems show a strongly mass-dependent behavior. The contrasting behavior of scrambled and unscrambled systems is described theoretically using a ''phase space'' partitioning factor. In scrambled systems an energetic asymmetric ozone isotopomer is accessed from both entrance channels and, as shown in paper I, the partitioning factor becomes unity throughout. In unscrambled systems, access to an asymmetric ozone is only from one entrance channel, and differences in zero-point energies and other properties, such as the centrifugal potential, determine the relative contributions ͑the partitioning factors͒ of the two exit channels to the lifetime of the resulting energetic ozone molecule. They are responsible for the large differences in individual recombination rate constants at low pressures. While the decrease in for symmetric systems is attributed to a small non-RRKM effect , these calculated results are independent of the exact origin of the decrease. The calculated ''mass-independent'' enrichments, ␦ and E, in scrambled systems are relatively insensitive to the transition state ͑TS͒, because of the absence of the partitioning factor in their case ͑for a fixed non-RRKM ͒. They are compared with the data at room temperature. Calculated results for the ratios of individual isotopomeric rate constants for the strongly mass-independent behavior for unscrambled systems are quite sensitive to the nature of the TS because of the partitioning effect. The current data are available only at room temperature but the loose TS is valid only at low temperatures. Accordingly, the results calculated for the latter at 140 K represent a prediction, for any given . At present, a comparison of the 140 K results can be made only with room temperature data. They show the same trends as, and are in fortuitous agreement, with the data. Work is in progress on a description appropriate for room temperature.

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Section: Discussionmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

Hathorn

Marcus

2000

The Journal of Chemical Physics

104

112

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“…This expression has been assumed in Ref. 27, and the P 1/2 can be obtained by fitting the experimental results of enrichment. The rate constant ratios given in Eqs.…”

Section: ͑45͒mentioning

confidence: 99%

“…There exist mainly two types of experimental observations: an unusual "mass-independent" isotopic fractionation ͑MIF͒ of ozone and a large unconventional highly "mass-dependent" isotope effect observed in the various rate constant ratios. [25][26][27][28][29] Rice-RamspergerKassel-Marcus ͑RRKM͒ theory with a master equation approach for the collisional deactivation of the intermediate excited ozone molecules has been applied to study both phenomena. [32][33][34] It was found that the MIF can be explained when an -effect, a non-RRKM effect, [30][31][32][33][34] which reduces dynamically the low-pressure rate constant of the recombination to form symmetric molecules by a factor of compared to that for the asymmetric ones, and a weak collision effect [32][33][34] for the deactivation of excited ozone molecules is also included in the theory.…”

Section: Introductionmentioning

confidence: 99%

An approximate theory of the ozone isotopic effects: Rate constant ratios and pressure dependence

Gao

Marcus

2007

The Journal of Chemical Physics

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The isotopic effects in ozone recombination reactions at low pressures are studied using an approximate theory which yields simple analytic expressions for the individual rate constant ratios, observed under "unscrambled" conditions. It is shown that the rate constant ratio between the two competing channels XYZ→ X + YZ and XYZ→ XY+ Z is mainly determined by the difference of the zero-point energies of diatomic molecules YZ and XY and by the efficiency of the deactivation of the newly formed excited ozone molecules, whereas the mass-independent fractionation depends on a "nonstatistical" symmetry factor and the collisional deactivation efficiency. Formulas for the pressure effects on the enrichment and on the rate constant ratios are obtained, and the calculated results are compared with experiments and more exact calculations. In all cases, ratios of isotope rates and the pressure dependence of enrichments, the agreement is good. While the initial focus was on isotope effects in the formation of O 3 , predictions are made for isotope effects on ratios of rate constants in other reactions such as O + CO → CO 2 , O+NO→ NO 2 , and O + SO → SO 2 .

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“…[10][11][12] _ENREF_13_ENREF_16 Numerous explanations for the unexpected enrichment have been offered in the literature since then. Isotope-dependent rates of ozone formation and the competing atom exchange reactions have been measured, [13][14][15][16] and the small change in reaction exoergicity due to the difference in zero-point energies of different isotopologues was proposed as a possible explanation for the unexpected isotope enrichment. However, zero-point energy effects may not be sufficient to alter ozone kinetics significantly, 16 leading to the conclusion that the isotope effect is dynamically driven.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the O-Atom Exchange Reaction ¹⁶O(³P) + ¹⁸O¹⁸O(³Σ_g^–) → ¹⁶O¹⁸O(³Σ_g^–) + ¹⁸O(³P) at Hyperthermal Energies

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Erratum: “Relative formation rates of O350 and O352 in O–16O18 mixtures” [J. Chem. Phys. 111, 7179 (1999)]

Cited by 24 publications

References 0 publications

An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

An approximate theory of the ozone isotopic effects: Rate constant ratios and pressure dependence

Dynamics of the O-Atom Exchange Reaction ¹⁶O(³P) + ¹⁸O¹⁸O(³Σ_g^–) → ¹⁶O¹⁸O(³Σ_g^–) + ¹⁸O(³P) at Hyperthermal Energies

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Erratum: “Relative formation rates of O350 and O352 in O–16O18 mixtures” [J. Chem. Phys. 111, 7179 (1999)]

Cited by 24 publications

References 0 publications

An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

An intramolecular theory of the mass-independent isotope effect for ozone. II. Numerical implementation at low pressures using a loose transition state

An approximate theory of the ozone isotopic effects: Rate constant ratios and pressure dependence

Dynamics of the O-Atom Exchange Reaction 16O(3P) + 18O18O(3Σg–) → 16O18O(3Σg–) + 18O(3P) at Hyperthermal Energies

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Dynamics of the O-Atom Exchange Reaction ¹⁶O(³P) + ¹⁸O¹⁸O(³Σ_g^–) → ¹⁶O¹⁸O(³Σ_g^–) + ¹⁸O(³P) at Hyperthermal Energies