Xu Chong, Wei Zhenxuan, Hu Huayu, Hu Xixi, Xie Daiqian
Kuang Yaming Honors School, Nanjing University, Nanjing 210023, China.
Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Molecules. 2024 Oct 18;29(20):4933. doi: 10.3390/molecules29204933.
Three-body recombination reactions, in which two particles form a bound state while a third one bounces off after the collision, play significant roles in many fields, such as cold and ultracold chemistry, astrochemistry, atmospheric physics, and plasma physics. In this work, the dynamics of the recombination reaction for the N system over a wide temperature range (5000-20,000 K) are investigated in detail using the quasi-classical trajectory (QCT) method based on recently developed full-dimensional potential energy surfaces. The recombination products are N() + N() in the 1″ state, N() + N() in the 2″ state, and N() + N() in both the 1″ and 2″ states. A three-body collision recombination model involving two sets of relative translational energies and collision parameters and a time-delay parameter is adopted in the QCT calculations. The recombination process occurs after forming an intermediate with a certain lifetime, which has a great influence on the recombination probability. Recombination processes occurring through a one-step three-body collision mechanism and two distinct two-step binary collision mechanisms are found in each state. And the two-step exchange mechanism is more dominant than the two-step transfer mechanism at higher temperatures. N() formed in all three related states is always the major recombination product in the temperature range from 5000 K to 20,000 K, with the relative abundance of N() increasing as temperature decreases. After hyperthermal collisions, the formed N(/) molecules are distributed in highly excited rotational and vibrational states, with internal energies mainly distributed near the dissociation threshold. Additionally, the rate coefficients for this three-body recombination reaction in each state are determined and exhibit a negative correlation with temperature. The dynamic insights presented in this work might be very useful to further simulate non-equilibrium dynamic processes in plasma physics involving N systems.
三体复合反应是指两个粒子形成束缚态，而第三个粒子在碰撞后反弹出去，这种反应在许多领域都起着重要作用，如冷化学和超冷化学、天体化学、大气物理学和等离子体物理学等。在这项工作中，基于最近开发的全维势能面，使用准经典轨迹（QCT）方法详细研究了N体系在很宽温度范围（5000 - 20000 K）内的复合反应动力学。复合产物为处于1″态的N() + N()、处于2″态的N() + N()以及同时处于1″态和2″态的N() + N()。在QCT计算中采用了一个涉及两组相对平动能量、碰撞参数和一个时间延迟参数的三体碰撞复合模型。复合过程在形成具有一定寿命的中间体后发生，这对复合概率有很大影响。在每个态中都发现了通过一步三体碰撞机制和两种不同的两步二元碰撞机制发生的复合过程。并且在较高温度下，两步交换机制比两步转移机制更占主导。在5000 K到20000 K的温度范围内，所有三个相关态中形成的N()始终是主要的复合产物，随着温度降低，N()的相对丰度增加。经过超热碰撞后，形成的N(/)分子分布在高激发转动和振动态，内能主要分布在离解阈值附近。此外，还确定了每个态中该三体复合反应的速率系数，并且它们与温度呈负相关关系。这项工作中呈现的动力学见解可能对进一步模拟等离子体物理学中涉及N体系的非平衡动态过程非常有用。
