Ion effect on the dynamics of water hydrogen bonding network: A theoretical and computational spectroscopy point of view

Understanding the elementary hydration dynamics of the ions and their couplings with the aqueous environments is important for researches in fields including energy, molecular biology, biomedical sciences, and chemical reactions. The concept of hydration shell is ubiquitously used to rationalize the differences of water behavior near the ions with respect to those in the bulk water. One intriguing issue, however, is to decide the spatial range of these hydration shells. Different experimental spectroscopic techniques such as the femtosecond infrared at high frequency and optical Kerr effect, dielectric relaxation, as well as terahertz measurements at low frequency often give controversial indications on this matter. As the optical transition observables provided by the spectroscopic measurements only indirectly reflect the real‐space structure and dynamics information, the theoretical modeling of these signals is often desired in order to reveal the underlying physics in each of these measurements, and to understand the aforementioned apparent controversy. In this review, we outline recent progresses in the theoretical modeling of water dynamics around the ions and ionic moieties and the related vibrational spectroscopy, especially on the femtosecond infrared related single molecular water reorientation and the low‐frequency vibrational spectra related collective water dynamics. This article is categorized under: Theoretical and Physical Chemistry > Spectroscopy Theoretical and Physical Chemistry > Statistical Mechanics