Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2946, USA.
J Chem Phys. 2019 Feb 21;150(7):074305. doi: 10.1063/1.5035283.
A vibrational state-specific model for dissociation and recombination reactions within the direct simulation Monte Carlo method is introduced to study the energy level dynamics of the O + O system. The state-resolved cross sections for vibrational relaxation and dissociation reactions are obtained from a rotationally averaged quasi-classical trajectory database based on the Varandas and Pais O( Σ )+O( P) potential energy surface. A two-step binary collision framework is outlined to characterize the vibrational state-resolved recombination probabilities, which are constrained by detailed balance for orbiting pair formation, and microscopic reversibility applied to the dissociation cross sections for orbiting pair stabilization. The vibrational state-to-state (STS) model is compared to the phenomenological total collision energy (TCE) and quantum kinetic (QK) models through a series of 0-d non-equilibrium relaxation calculations. A quasi-steady state (QSS) region is established in the vibrational temperature profiles of the TCE, QK, and STS models under non-equilibrium heating. This QSS region is a result of the competition between vibrational relaxation by vibrational-translational (VT) transitions and O dissociation. The duration of QSS predicted by the STS model is approximately ten and four times that of the TCE and QK model predictions, respectively, and the total time to reach equilibrium is approximately 3.5 times that of the TCE model and 1.5 times that of the QK model. A distinct QSS region is not observed in the non-equilibrium cooling case. This is attributed to the relatively rapid VT transitions that work to equilibrate the vibrational energy distribution upon recombination, which is comparatively slow. The total time to reach equilibrium by the STS model in the non-equilibrium cooling case is five times and three times greater than those of the QK and TCE models, respectively.
本文引入了一种振动态特异的离解和复合反应模型，用于研究 O + O 体系的能级动力学。基于 Varandas 和 Pais O( Σ )+O( P)势能面，从旋转平均拟经典轨迹数据库中获得了振动弛豫和离解反应的态分辨截面。概述了两步二进制碰撞框架，以描述振动态分辨复合概率，该概率由轨道对形成的详细平衡以及轨道对稳定化的离解截面的微观可逆性来约束。通过一系列 0-d 非平衡弛豫计算，将振动态到态（STS）模型与唯象总碰撞能量（TCE）和量子动力学（QK）模型进行了比较。在非平衡加热下，TCE、QK 和 STS 模型的振动温度分布中建立了准稳态（QSS）区域。该 QSS 区域是振动弛豫通过振动-平移（VT）跃迁和 O 离解之间竞争的结果。STS 模型预测的 QSS 持续时间分别约为 TCE 和 QK 模型预测的 10 倍和 4 倍，达到平衡的总时间分别约为 TCE 模型的 3.5 倍和 QK 模型的 1.5 倍。在非平衡冷却情况下，没有观察到明显的 QSS 区域。这归因于相对较快的 VT 跃迁，它在复合时有助于平衡振动能分布，而复合相对较慢。在非平衡冷却情况下，STS 模型达到平衡的总时间分别比 QK 和 TCE 模型长 5 倍和 3 倍。
