Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands.
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
Nat Chem. 2018 Apr;10(4):435-440. doi: 10.1038/s41557-018-0001-3. Epub 2018 Feb 19.
Over the last 25 years, the formalism known as coupled-cluster (CC) theory has emerged as the method of choice for the ab initio calculation of intermolecular interaction potentials. The implementation known as CCSD(T) is often referred to as the gold standard in quantum chemistry. It gives excellent agreement with experimental observations for a variety of energy-transfer processes in molecular collisions, and it is used to calibrate density functional theory. Here, we present measurements of low-energy collisions between NO radicals and H molecules with a resolution that challenges the most sophisticated quantum chemistry calculations at the CCSD(T) level. Using hitherto-unexplored anti-seeding techniques to reduce the collision energy in a crossed-beam inelastic-scattering experiment, a resonance structure near 14 cm is clearly resolved in the state-to-state integral cross-section, and a unique resonance fingerprint is observed in the corresponding differential cross-section. This resonance structure discriminates between two NO-H potentials calculated at the CCSD(T) level and pushes the required accuracy beyond the gold standard.
在过去的 25 年中，被称为耦合簇（CC）理论的形式主义已经成为从头计算分子间相互作用势的首选方法。被称为 CCSD(T)的实现通常被称为量子化学中的金标准。它在分子碰撞中的各种能量转移过程中与实验观察结果非常吻合，并且被用来校准密度泛函理论。在这里，我们使用迄今为止尚未开发的反播种技术来降低交叉束非弹性散射实验中的碰撞能量，在态-态积分截面中清楚地分辨出 14cm 附近的共振结构，并在相应的微分截面中观察到独特的共振指纹。这种共振结构可以区分在 CCSD(T)水平下计算的两种 NO-H 势能，并将所需的精度推到金标准之外。
