Quantum state-to-state dynamics studies of the C(3P) + OH(X2Π) → CO(a3Π) + H(2S) reaction based on a new HCO(12A″) potential energy surface

Abstract

Using the multi-reference configuration interaction method with the aug-cc-pV(Q/5)Z basis set, 7762 ab initio energy points were computed and used to construct an analytical potential energy surface (PES) for HCO(12A″). The fitted PES has an overall root-mean-square deviation of 0.833 kcal/mol. Based on this PES, the geometry, energy, and harmonic frequencies of stationary points were analyzed in detail, showing good agreement with other theoretical data. Subsequently, quantum time-dependent wave packet (TDWP) and quasi-classical trajectory (QCT) calculations were performed on this new PES to study the reaction C(3P) + OH(X2Π) → CO(a3Π) + H(2S). The reaction probabilities, integral cross sections, differential cross sections, product rot-vibrational distributions, and rate constants were obtained. TDWP results show a rich resonance structure, and the QCT calculations provide a qualitatively correct description of the reaction cross section. Discrepancies between the dynamical information derived from the two methods indicate pronounced quantum effects in this reaction. The reaction is predominantly governed by a complex-forming mechanism. Although increasing collision energy shortens the complex lifetime, the indirect mechanism remains operative across the studied energy range. This study provides fundamental insights into the microscopic reaction mechanisms and dynamics of carbon chemistry in interstellar environments and provides theoretical support for future experimental results.