We report the results of two sets of experiments on each of the reactions
and
In low temperature (15–295 K) kinetic experiments performed in a CRESU (Cinétique de Réaction en
Ecoulement Supersonique Uniforme) apparatus, the rate constants for these two reactions were found to fit the
following expressions:
and
In crossed beam experiments, relative cross-sections for products of the two reactions [CO from (1) and CN
from (2a)] in specific vibrational levels were measured at collision energies (εtr) between ca. 4 and 100 meV. The
cross-sections are proportional to (εtr)−0.94 for reaction (1) and to (εtr)−0.72 for reaction (2a). Both sets of results
demonstrate that these reactions proceed over potential energy surfaces with no barrier on the path from
reactants to products. If the reaction cross-sections are independent of the rotational energy level of the
reagents and of the distribution of C(3PJ) atoms over spin–orbit states, and if they exhibit the same dependence
on relative translational energy below 4 meV as above, integration of the excitation functions leads to the rate
constants exhibiting temperature dependences of k1(T) proportional to T−0.44 and k2a(T) proportional to
T−0.22, in reasonable agreement with the direct measurements of the rate constants for reactions (1) and (2).
The two sets of experimental results are also compared with theoretical calculations, based on the adiabatic
capture centrifugal sudden approximation (ACCSA) model. The calculations correctly predict the temperature
dependence of the rate constants for both reactions. The consistency of these three data sets is discussed.
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