Accurate High-Level Ab Initio-Based Global Potential Energy Surface and Quantum Dynamics Calculation for the First Excited State of CH2.

A full three-dimensional global potential energy surface (PES), covering the whole configuration space, is reported first for the title system by fitting high-level ab initio energies at the multireference configuration interaction level with the aug-cc-pV6Z basis set. In this work, the many-body expansion method is invoked to fit the innate character of the CH2+(12A″) PES. The topographical features are examined in detail based on the new global PES and in accordance with the other calculations from the ab initio energies, which show the correct behavior at the C+(2P) + H2(X1Σg+) and CH+(a3Π) + H(2S) dissociation limits. Using a time-dependent wave packet method, we provide insights into the dynamics behavior for reaction of C+(2P) + H2(X1Σg+) → CH+(a3Π) + H(2S). The integral cross sections and reaction probabilities increase monotonically in terms of the collision energy.