TY - JOUR
T1 - Reanalysis of Rate Data for the Reaction CH3 + CH3 → C2H6 Using Revised Cross Sections and a Linearized Second-Order Master Equation
AU - Blitz, Mark A.
AU - Green, Nicholas J. B.
AU - Shannon, Robin J.
AU - Pilling, Michael J.
AU - Seakins, Paul W.
AU - Western, Colin M.
AU - Robertson, Struan H.
PY - 2015/7/16
Y1 - 2015/7/16
N2 - Rate coefficients for the CH3 + CH3 reaction, over
the temperature range 300–900 K, have been corrected for errors in the
absorption coefficients used in the original publication (Slagle et al., J. Phys. Chem. 1988, 92, 2455−2462). These corrections necessitated the development of a detailed model of the B̃2A1′ (3s)–X̃2A2″ transition in CH3
and its validation against both low temperature and high temperature
experimental absorption cross sections. A master equation (ME) model was
developed, using a local linearization of the second-order decay, which
allows the use of standard matrix diagonalization methods for the
determination of the rate coefficients for CH3 + CH3. The ME model utilized inverse Laplace transformation to link the microcanonical rate constants for dissociation of C2H6 to the limiting high pressure rate coefficient for association, k∞(T); it was used to fit the experimental rate coefficients using the Levenberg–Marquardt algorithm to minimize χ2 calculated from the differences between experimental and calculated rate coefficients. Parameters for both k∞(T) and for energy transfer ⟨ΔE⟩down(T)
were varied and optimized in the fitting procedure. A wide range of
experimental data were fitted, covering the temperature range 300–2000
K. A high pressure limit of k∞(T) = 5.76 × 10–11(T/298 K)−0.34 cm3 molecule–1 s–1 was obtained, which agrees well with the best available theoretical expression.
AB - Rate coefficients for the CH3 + CH3 reaction, over
the temperature range 300–900 K, have been corrected for errors in the
absorption coefficients used in the original publication (Slagle et al., J. Phys. Chem. 1988, 92, 2455−2462). These corrections necessitated the development of a detailed model of the B̃2A1′ (3s)–X̃2A2″ transition in CH3
and its validation against both low temperature and high temperature
experimental absorption cross sections. A master equation (ME) model was
developed, using a local linearization of the second-order decay, which
allows the use of standard matrix diagonalization methods for the
determination of the rate coefficients for CH3 + CH3. The ME model utilized inverse Laplace transformation to link the microcanonical rate constants for dissociation of C2H6 to the limiting high pressure rate coefficient for association, k∞(T); it was used to fit the experimental rate coefficients using the Levenberg–Marquardt algorithm to minimize χ2 calculated from the differences between experimental and calculated rate coefficients. Parameters for both k∞(T) and for energy transfer ⟨ΔE⟩down(T)
were varied and optimized in the fitting procedure. A wide range of
experimental data were fitted, covering the temperature range 300–2000
K. A high pressure limit of k∞(T) = 5.76 × 10–11(T/298 K)−0.34 cm3 molecule–1 s–1 was obtained, which agrees well with the best available theoretical expression.
U2 - 10.1021/acs.jpca.5b01002
DO - 10.1021/acs.jpca.5b01002
M3 - Article
C2 - 25992467
VL - 119
SP - 7668
EP - 7682
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 28
ER -