Larsson Henrik R, Viel Alexandra
Department of Chemistry and Biochemistry, University of California, Merced, CA 95343, USA. NO3a[at]larsson-research.δe.
Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France. alexandra.viel[at]univ-rennes1.fr.
Phys Chem Chem Phys. 2024 Sep 25;26(37):24506-24523. doi: 10.1039/d4cp02653e.
The nitrate radical NO plays an important role in atmospheric chemistry, yet many aspects of its coupled and anharmonic vibronic structure remain elusive. Here, using an accurate, coupled full-dimensional diabatic potential that includes five electronic states, we revisit the vibronic spectrum associated with the electronic state. Using recently developed tensor network state methods, we are able to compute more than 2500 vibronic states, thereby increasing the number of computed full-dimensional states by a factor of 50, compared to previous work. While we obtain good agreement with experiment for most of the assigned vibronic levels, for several others, we observe striking disagreement. Further, for the antisymmetric bending motion we find remarkably large symmetry-induced level splittings that are larger than the zero-order reference. We discuss non-negligible nonadiabatic effects and show that the Born-Oppenheimer approximation leads to significant errors in the spectrum.
硝酸根自由基NO在大气化学中起着重要作用，但其耦合和非谐振动电子结构的许多方面仍然难以捉摸。在这里，我们使用一个精确的、包含五个电子态的耦合全维 diabatic 势，重新审视与该电子态相关的振动光谱。使用最近开发的张量网络态方法，我们能够计算出超过2500个振动态，从而使计算出的全维态数量比之前的工作增加了50倍。虽然我们对大多数已指定的振动态与实验结果取得了良好的一致性，但对于其他几个态，我们观察到了显著的差异。此外，对于反对称弯曲运动，我们发现了非常大的对称诱导能级分裂，其大于零阶参考值。我们讨论了不可忽略的非绝热效应，并表明玻恩-奥本海默近似在光谱中导致了显著的误差。
