Yang Benhui, Qu Chen, Bowman J M, Yang Dongzheng, Guo Hua, Balakrishnan N, Forrey R C, Stancil P C
Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, Georgia 30602, United States.
Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States.
J Phys Chem Lett. 2024 Nov 14;15(45):11312-11319. doi: 10.1021/acs.jpclett.4c02865. Epub 2024 Nov 4.
The rovibrational level populations, and subsequent emission in various astrophysical environments, are driven by inelastic collision processes. The available rovibrational rate coefficients for water have been calculated using a number of approximations. We present a numerically exact calculation for the rovibrational quenching for all water vibrational modes due to collisions with atomic hydrogen. The scattering theory implements a quantum close-coupling (CC) method on a high level ab initio six-dimensional (6D) potential energy surface (PES). Total rovibrational quenching cross sections for excited bending levels were compared with earlier results on a 4D PES with the rigid-bender close-coupling (RBCC) approximation. General agreement between 6D-CC and 4D-RBCC calculations are found, but differences are evident including the energy and amplitude of low-energy orbiting resonances. Quenching cross sections from the symmetric and asymmetric stretch modes are provided for the first time. The current 6D-CC calculation provides accurate inelastic data needed for astrophysical modeling.
振转能级布居以及随后在各种天体物理环境中的发射是由非弹性碰撞过程驱动的。水的可用振转速率系数已通过多种近似方法计算得出。我们给出了由于与氢原子碰撞导致的所有水振动模式的振转猝灭的数值精确计算。散射理论在高水平的从头算六维（6D）势能面（PES）上采用量子密耦（CC）方法。将激发弯曲能级的总振转猝灭截面与早期在具有刚性弯曲密耦（RBCC）近似的4D PES上的结果进行了比较。发现6D-CC和4D-RBCC计算之间总体一致，但差异明显，包括低能轨道共振的能量和幅度。首次给出了对称和不对称伸缩模式的猝灭截面。当前的6D-CC计算提供了天体物理建模所需的精确非弹性数据。
