Theoretical Sensitivity of the C(3P) + OH(X2Π) → CO(X1Σ+) + H(2S) Rate Constant: The Role of the Long-Range Potential

Faced with the lack of experimental data on the C(P-3) + OH(X-2 Pi) -> CO(X-1 Sigma(+)) + H(S-2) reaction, we propose here to compare rate constant values and their behavior with temperature following various dynamical models and, in particular, to check the sensivity of these quantities with the long-range part of the potential energy surface. For that, we have evaluated the C + OH rate constant using the quasiclassical trajectory (QCT) method, the adiabatic capture centrifugal sudden approximation (ACCSA), and the mean potential capture theory (MPCT) based on a full ab initio potential energy surface fitted with q(1)(2, 5) kernels or on a perturbative multipolar expansion (MPE) potential including the monomer spin orbit splittings (MPE-SO) or not. Despite the various approximations involved in the different methods and PESs, an excellent agreement is obtained in a subset of three models: the ACCSA method with PME-SO or ab initio PESs and the QCT method with the latter PES. This suggests that the reaction takes place once the system enters the deep valley of products. In that case, the errors due to these approximate methods and PESs are small and, consequently, the rate constants are accurately calculated. Furthermore, these findings provide evidence of preponderance of the entrance channel in the reactivity of this system.