Theoretical Chemistry and Biology, Royal Institute of Technology, 10691, Stockholm, Sweden.
Laboratory for Nonlinear Optics and Spectroscopy, Siberian Federal University, 660041, Krasnoyarsk, Russia.
Nat Commun. 2019 Mar 4;10(1):1013. doi: 10.1038/s41467-019-08979-4.
Local probes of the electronic ground state are essential for understanding hydrogen bonding in aqueous environments. When tuned to the dissociative core-excited state at the O1s pre-edge of water, resonant inelastic X-ray scattering back to the electronic ground state exhibits a long vibrational progression due to ultrafast nuclear dynamics. We show how the coherent evolution of the OH bonds around the core-excited oxygen provides access to high vibrational levels in liquid water. The OH bonds stretch into the long-range part of the potential energy curve, which makes the X-ray probe more sensitive than infra-red spectroscopy to the local environment. We exploit this property to effectively probe hydrogen bond strength via the distribution of intramolecular OH potentials derived from measurements. In contrast, the dynamical splitting in the spectral feature of the lowest valence-excited state arises from the short-range part of the OH potential curve and is rather insensitive to hydrogen bonding.
研究水中氢键作用，对其电子基态进行局域探测是十分必要的。当调谐到水的 O1s 预边缘的离解芯激发态时，由于超快核动力学，回到电子基态的共振非弹性 X 射线散射表现出长的振动进展。我们展示了围绕芯激发氧的 OH 键的相干演化如何为液体水中的高振动能级提供通道。OH 键拉伸到势能曲线的远程部分，这使得 X 射线探针比红外光谱对局部环境更敏感。我们利用这一特性，通过从测量中得出的分子内 OH 势能分布，有效地探测氢键强度。相比之下，最低价激发态谱特征中的动力学分裂来自 OH 势能曲线的短程部分，并且对氢键不太敏感。
