He Dong, Hong Qizhen, Li Fei, Sun Quanhua, Si Ting, Luo Xisheng
Deep Space Exploration Laboratory, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230026, People's Republic of China.
State Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
J Chem Phys. 2023 Dec 21;159(23). doi: 10.1063/5.0176176.
The time-dependent rotational and vibrational temperatures were measured to study the shock-heated thermal nonequilibrium behaviors of CO with Ar, He, and H2 as collision partners. Three interference-free transition lines in the fundamental vibrational band of CO were applied to the fast, in situ, and state-specific measurements. Vibrational relaxation times of CO were summarized over a temperature range of 1110-2820 K behind reflected shocks. The measured rotational temperature instantaneously reached an equilibrium state behind shock waves. The measured vibrational temperature experienced a relaxation process before reaching the equilibrium state. The measured vibrational temperature time histories were compared with predictions based on the Landau-Teller model and the state-to-state approach. The state-to-state approach treats the vibrational energy levels of CO as pseudo-species and accurately describes the detailed thermal nonequilibrium processes behind shock waves. The datasets of state-specific inelastic rate coefficients of CO-Ar, CO-He, CO-CO, and CO-H2 collisions were calculated in this study using the mixed quantum-classical method and the semiclassical forced harmonic oscillator model. The predictions based on the state-to-state approach agreed well with the measured data and nonequilibrium (non-Boltzmann) vibrational distributions were found in the post-shock regions, while the Landau-Teller model predicted slower vibrational temperature time histories than the measured data. Modifications were applied to the Millikan-White vibrational relaxation data of the CO-Ar and CO-H2 systems to improve the performance of the Landau-Teller model. In addition, the thermal nonequilibrium processes behind incident shocks, the acceleration effects of H2O on the relaxation process of CO, and the characterization of vibrational temperature were highlighted.
测量了随时间变化的转动温度和振动温度，以研究以氩气、氦气和氢气作为碰撞伙伴时一氧化碳的激波加热热非平衡行为。一氧化碳基频振动带中的三条无干扰跃迁线被用于快速、原位和态分辨测量。总结了在反射激波后1110 - 2820 K温度范围内一氧化碳的振动弛豫时间。测量的转动温度在激波后瞬间达到平衡状态。测量的振动温度在达到平衡状态之前经历了一个弛豫过程。将测量的振动温度随时间变化的历史与基于朗道 - 泰勒模型和态 - 态方法的预测进行了比较。态 - 态方法将一氧化碳的振动能级视为准物种，并准确描述了激波后详细的热非平衡过程。本研究使用混合量子 - 经典方法和半经典强迫谐振子模型计算了一氧化碳 - 氩气、一氧化碳 - 氦气、一氧化碳 - 一氧化碳和一氧化碳 - 氢气碰撞的态分辨非弹性速率系数数据集。基于态 - 态方法的预测与测量数据吻合良好，并且在激波后区域发现了非平衡（非玻尔兹曼）振动分布，而朗道 - 泰勒模型预测的振动温度随时间变化的历史比测量数据慢。对一氧化碳 - 氩气和一氧化碳 - 氢气系统的米利肯 - 怀特振动弛豫数据进行了修正，以提高朗道 - 泰勒模型的性能。此外，还强调了入射激波后的热非平衡过程、水对一氧化碳弛豫过程的加速作用以及振动温度的表征。
