N. Marchand et al., THEORETICAL-STUDY OF THE REACTION CH(X-2-PI)-2-PI) - 3 - DETERMINATION OF THE BRANCHING RATIOS(NO(X), The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(19), 1998, pp. 3358-3367
In this paper, which is the third of a series devoted to the title rea
ction, we present theoretical calculations of branching ratios for the
product channels involved in the reaction. In the first paper of this
series (Marchand, N.; Jimeno, P.; Rayez, J. C.; Liotard, D. J. Phys.
Chem. 1997, 1O1, 6077.), we explored the topology of the lowest triple
t potential energy surface determined with sophisticated ab initio met
hods and proposed several reaction paths connecting the reactants to t
he products. We have used these results to determine the branching rat
ios using two methods based on multichannel Rice-Ramsperger-Kassel-Mar
cus (RRKM) calculations: a mu VTST/RRKM (mu VTST = microcanonical vari
ational transition state theory) method developed by one of us and an
ACIOSA/RRKM (ACIOSA = adiabatic capture model using the infinite order
sudden approximation) method dealing with a capture rate constant cal
culation (Marchand, N.; Stoecklin, T.; Rayez, J. C. To be submitted, o
f this series). Our present results reveal that, at 300 K, HCN + O is
the major product channel involved in the reaction (72.0%), the other
branching ratios being 13.9% for NCO + H, 8.2% for CO + NH, 3.3% for C
NO + H, and 1.4% for CN + OH. All the others channels contribute for l
ess than 1% each. These theoretical results are in agreement with the
results of several experimental studies, especially those very recentl
y obtained in our laboratory by Bergeat et al. Moreover, we observe no
significant temperature dependence of the branching ratios.