Denis-Alpizar Otoniel, Unke Oliver T, Bemish Raymond J, Meuwly Markus
Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
Phys Chem Chem Phys. 2017 Oct 25;19(41):27945-27951. doi: 10.1039/c7cp05036d.
The collision of N with Ar is studied using quantum and classical methods. The dynamics was followed on a new potential energy surface based on ab initio energies computed at the UCCSD(T)-F12a/aug-cc-pVTZ level, using the correct analytical long range behaviour and a reproducing kernel representation. Comparison with multi-reference MRCI+Q calculations establish that UCCSD(T)-F12a is a sufficiently high level of theory for this problem. Results from quantum close coupling and quasiclassical trajectory calculations agree favourably with each other and the rates for inelastic collisions are lower than those from Langevin theory. This differs from previous calculations on a zero point-corrected potential energy surface (PES) and indicates that such corrections, although potentially useful, should not be applied in the present case. Despite the rather large differences between the potential energy surfaces, the computed rates are within one order of magnitude of one another which suggests that the quality of the PES is not the main reason for the remaining disagreement between computation and experiment. Also, the fraction of inelastic rotational collisions exceeds 20% in all cases irrespective of whether quantum or classical dynamics is used. Previous experimental rate coefficients for N(ν = 0, j = 6) colliding with Ar suggest that the rotational quantum number is largely conserved. This can not be confirmed from any of the simulations and calls for new single molecule experiments.
利用量子和经典方法研究了N与Ar的碰撞。动力学过程是在一个基于UCCSD(T)-F12a/aug-cc-pVTZ水平计算的从头算能量的新势能面上进行跟踪的，该势能面使用了正确的解析长程行为和再生核表示。与多参考MRCI+Q计算的比较表明，UCCSD(T)-F12a对于这个问题是一个足够高的理论水平。量子密耦和准经典轨迹计算的结果彼此吻合良好，非弹性碰撞的速率低于朗之万理论计算的速率。这与之前在零点校正势能面（PES）上的计算结果不同，表明这种校正虽然可能有用，但在当前情况下不应应用。尽管势能面之间存在相当大的差异，但计算得到的速率在一个数量级以内，这表明PES的质量不是计算结果与实验结果之间仍存在分歧的主要原因。此外，无论使用量子动力学还是经典动力学，在所有情况下非弹性转动碰撞的比例都超过20%。之前关于N(ν = 0, j = 6)与Ar碰撞的实验速率系数表明，转动态量子数在很大程度上是守恒的。但在任何模拟中都无法证实这一点，因此需要进行新的单分子实验。
