Chen Jun, Li Jun, Bowman Joel M, Guo Hua
Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China.
J Chem Phys. 2020 Aug 7;153(5):054310. doi: 10.1063/5.0015101.
Energy transfer between vibrational modes can be quite facile, and it has been proposed as the dominant mechanism for energy pooling in extreme environments such as nonthermal plasmas and laser cavities. To understand such processes, we perform quasi-classical trajectory studies of CO(v) + CO(v) collisions on a new full-dimensional potential energy surface fit to high-level ab initio data using a neural network method and examine the key vibrational energy transfer channels. In addition to the highly efficient CO(v + 1) + CO(v - 1) channel, there exists a significant, sometimes dominant, CO(v + 2) + CO(v - 2) channel for large v states at low collision energies. The latter is shown to stem from the substantially increased interaction between highly vibrationally excited CO, which has a much larger dipole moment than at its equilibrium bond length. Finally, the vibrational state-specific cross sections and their energy dependence on the thermal range are predicted from a limited dataset using Gaussian process regression. The relevance of these results to plasma chemistry and laser engineering and the recently observed flipping of highly vibrationally excited CO adsorbates on a cold NaCl surface is discussed.
振动模式之间的能量转移可能相当容易，并且它已被提出作为在非热等离子体和激光腔等极端环境中能量汇聚的主要机制。为了理解此类过程，我们在一个使用神经网络方法拟合到高水平从头算数据的新的全维势能面上，对CO(v) + CO(v)碰撞进行准经典轨迹研究，并研究关键的振动能量转移通道。除了高效的CO(v + 1) + CO(v - 1)通道外，在低碰撞能量下，对于大v态还存在一个显著的、有时占主导的CO(v + 2) + CO(v - 2)通道。结果表明，后者源于高振动激发的CO之间相互作用的大幅增加，这种CO的偶极矩比其平衡键长时大得多。最后，使用高斯过程回归从有限的数据集中预测了特定振动状态的截面及其在热范围内的能量依赖性。讨论了这些结果与等离子体化学和激光工程的相关性，以及最近观察到的高振动激发的CO吸附物在冷NaCl表面上的翻转。
