1] Université de Bordeaux, Institut des Sciences Moléculaires, Talence Cedex 33405, France [2] CNRS, UMR 5255, Talence Cedex 33405, France.
Radboud University Nijmegen, Institute for Molecules and Materials, Heijendaalseweg 135, Nijmegen 6525 AJ, The Netherlands.
Nat Chem. 2015 Apr;7(4):349-53. doi: 10.1038/nchem.2204.
In molecular collisions, long-lived complexes may be formed that correspond to quasi-bound states in the van der Waals potential and give rise to peaks in the collision energy-dependent cross-sections. They are known as 'resonances' and their experimental detection remains difficult because their signatures are extremely challenging to resolve. Here, we show a complete characterization of quantum-dynamical resonances occurring in CO-He inelastic collisions with rotational CO(j = 0->1) excitation. Crossed-beam scattering experiments were performed at collision energies as low as 4 cm(-1), equivalent to a temperature of 4 K. Resonance structures in the measured cross-sections were identified by comparison with quantum-mechanical calculations. The excellent agreement found confirms that the potential energy surfaces describing the CO-He van der Waals interaction are perfectly suitable for calculating state-to-state (de)excitation rate coefficients at the very low temperatures needed in chemical modelling of the interstellar medium. We also computed these rate coefficients.
在分子碰撞中，可能会形成对应于范德华势能中的准束缚态的长寿命复合物，并在碰撞能量相关的截面中产生峰。它们被称为“共振”，但由于其特征非常难以分辨，因此其实验检测仍然很困难。在这里，我们展示了在 CO-He 非弹性碰撞中发生的量子动力学共振的完整特征，其中 CO(j = 0->1)激发。在碰撞能量低至 4 cm(-1)（相当于 4 K 的温度）下进行了交叉束散射实验。通过与量子力学计算的比较，确定了测量截面中的共振结构。所发现的极好一致性证实了描述 CO-He 范德华相互作用的势能面非常适合在星际介质化学模型中计算非常低温度下的状态到状态（去）激发率系数。我们还计算了这些速率系数。
