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Rotational state-to-state transition rate coefficients for H2O + H2O collisions at nonequilibrium conditions
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-08-22 , DOI: 10.1051/0004-6361/202450738
Bikramaditya Mandal , Michal Zoltowski , Martin Cordiner , Francois Lique , Dmitri Babikov

Aims. The goal is to develop a database of rate coefficients for rotational state-to-state transitions in H2O + H2O collisions that is suitable for the modeling of energy transfer in nonequilibrium conditions, in which the distribution of rotational states of H2O deviates from local thermodynamic equilibrium.Methods. A two-temperature model was employed that assumed that although there is no equilibrium between all possible degrees of freedom in the system, the translational and rotational degrees of freedom can be expected to achieve their own equilibria independently, and that they can be approximately characterized by Boltzmann distributions at two different temperatures, Tkin and Trot.Results. Upon introducing our new parameterization of the collisional rates, taking into account their dependence on both Tkin and Trot, we find a change of up to 20% in the H2O rotational level populations for both ortho and para-H2O for the part of the cometary coma where the nonequilibrium regime occurs.

中文翻译:


非平衡条件下 H2O + H2O 碰撞的旋转态到态转变速率系数



目标。目标是开发一个 H2O + H2O 碰撞中旋转状态到状态转变的速率系数数据库,该数据库适用于非平衡条件下的能量转移建模,其中 H2O 旋转状态的分布偏离局部热力学平衡。方法。采用双温度模型,假设虽然系统中所有可能的自由度之间不存在平衡,但平移和旋转自由度可以预期独立地达到各自的平衡,并且它们可以近似地表征为两种不同温度(Tkin 和 Trot)下的玻尔兹曼分布。结果。在引入新的碰撞率参数化后,考虑到它们对 Tkin 和 Trot 的依赖性,我们发现彗发部分的正 H2O 和对 H2O 的 H2O 旋转能级总体变化高达 20%非平衡状态发生的地方。
更新日期:2024-08-23