Kinetic isotope effects: Theoretical prediction of the thermal rate coefficient for the reaction D+O/sub 2/. -->. OD+O
Quasiclassical trajectory (QCT) and quasiclassical trajectory quantum mechanical threshold (QCT--QMT) calculations are reported for the reaction D+O/sub 2/..-->..OD+O. The thermal rate coefficient from the QCT--QMT analysis was determined to be k/sub 2/ = 8.12 x 10/sup 15/T/sup -0.659/ exp(-15 041/RT) cm/sup 3//mol s, for 250<2500 K, in excellent agreement with the experimental results available. Comparing with the QCT--QMT result (J. Chem. Phys. 74, 5120 (1981)) for (R1) H+O/sub 2/..-->..OH+O, the ratio k/sub 2//k/sub 1/ is found to vary from 7.5 at 250 K to 0.8 at 2500 K. The primary isotope effects controlling this difference are the difference in zero-point vibrational energies of the product diatoms at low temperature and the difference in reactant collision frequencies at high temperature. In addition the calculations show slightly less negative Arrhenius curvature (n/sub 2/ = -0.659, n/sub 1/ = -0.816) for R2 than for R1, an effect anticipated from the previous analysis. However, the magnitude of the difference between n/sub 1/ and n/sub 2/ is approximately the same as estimates of the maximum uncertainty in the calculations themselves. It is concluded that a factor of 2 in the mass of the attacking atom is not sufficient to distinguish accurately differences in Arrhenius curvature arising from the L+HH mass combination of the reactants, either theoretically or experimentally.
- Research Organization:
- Combustion Physics Division, Sandia National Laboratories, Livermore, California 94550
- OSTI ID:
- 6087621
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 75:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHEMICAL REACTION KINETICS
ISOTOPE EFFECTS
DEUTERIUM
OXYGEN
HIGH TEMPERATURE
MEDIUM TEMPERATURE
TEMPERATURE DEPENDENCE
VERY HIGH TEMPERATURE
ELEMENTS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
NONMETALS
NUCLEI
ODD-ODD NUCLEI
REACTION KINETICS
STABLE ISOTOPES
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation