Seminars Archive

Terahertz-driven dynamics in liquid water

Abstract
On the microscopic scale, water molecules in the liquid phase make hydrogen bonds with tetrahedral structures that fluctuate on the picosecond (ps) timescale. On the macroscopic scale, thermo-dynamic properties of liquid water, such as density and compressibility, are anomalous as they scale non-continuously. However, it is unclear how the macroscopic behavior emerges from the microscopic properties. An inherently powerful spectroscopic tool to study liquid water is terahertz (THz) radiation because it can reveal the fluctuations of the water network on the picosecond time scale, which are of the same order of magnitude of the relaxation time constants. In fact, THz radiation between about 1 and 25 THz is strongly absorbed by the intermolecular collective modes of liquid water. Recent advances in non-linear THz spectroscopy have revealed large signals from water. Among the different, competing models, here I show that the resonant reorientation of hydrogen-bonded water molecules might be the most appropriate to describe all of the currently available experimental results. Furthermore, I will discuss how aqueous salt solutions be turned into excellent electrical conductors at terahertz frequencies for an ultra-short amount of time. References Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths Materials 13, 1311 (2020) Strong Anisotropy in Liquid Water upon Librational Excitation Using Terahertz Laser Fields J. Phys. Chem. B 124, 4989 (2020) Nonlinear TeraHertz Transmission by Liquid Water at 1 THz Appl. Sci. 10, 5290 (2020) Terahertz pump–probe of liquid water at 12.3 THz Phys. Chem. Chem. Phys. 24, 653 (2022) Temperature-independent non-linear terahertz transmission by liquid water AIP Advances 12, 115319 (2022) An ultra-fast liquid switch for terahertz radiation. APL Photonics 7, 121302 (2022) The birth and evolution of solvated electrons in the water. PNAS, in press (2023)