Wiesenfeld Laurent
Laboratoire Aimé-Cotton, CNRS and Université Paris-Saclay, 91405 Orsay, France.
J Chem Phys. 2022 Nov 7;157(17):174304. doi: 10.1063/5.0102279.
We present here the first full computation of the rovibrational quenching of a polyatomic molecule (water) by a rotating molecular projectile (H). The computation is performed for quenching from the first bending mode of water at ν ≃ 1595 cm with a rotation energy of up to ∼400 cm in the bending mode. Molecular hydrogen is in its para and ortho modifications; it is rotating with a rotational quantum number of up to 4 and 3, respectively. All computations are performed on a very reliable and fully tested potential water-hydrogen energy surface of full dimensionality. Dynamics is performed in the full coupled channel formalism in the rigid bender approximation with a decoupling of the water rotation and vibration bases. Rate coefficients are converged for a kinetic temperature range 50-500 K. The crucial importance of the proper treatment of the projectile rotation is emphasized with orders of magnitude differences between the different channels for the H rotation. Sensitivity to the actual rovibrational initial state of water exists but in a weaker manner. Overall quenching rate coefficients are about 10 cm s, remaining one to three orders of magnitude lower than pure rotational quenching. They should be employed to model denser and warmer astrophysical media, such as high atmospheres or star and planet forming regions, which are to be explored by infrared space telescopes, such as JWST.
我们在此展示了多原子分子（水）被旋转分子射体（氢原子）进行振转猝灭的首次完整计算。该计算针对水在ν≃1595 cm处的第一弯曲模式进行猝灭，弯曲模式下旋转能量高达约400 cm。分子氢处于仲氢和正氢构型；其旋转量子数分别高达4和3。所有计算均基于一个非常可靠且经过充分测试的全维度水 - 氢能量表面进行。动力学计算采用全耦合通道形式，在刚性弯曲近似下，水的转动和振动基进行解耦。速率系数在50 - 500 K的动力学温度范围内收敛。对于氢原子的转动，不同通道之间存在数量级差异，这突出了正确处理射体转动的至关重要性。对水的实际振转初始状态存在敏感性，但程度较弱。总体猝灭速率系数约为10 cm³ s⁻¹，仍比纯转动猝灭低一到三个数量级。它们应用于对密度更高、温度更高的天体物理介质进行建模，例如高层大气或恒星与行星形成区域，这些区域将由诸如詹姆斯·韦伯太空望远镜（JWST）等红外空间望远镜进行探测。
