Coupling between molecular rotations and OH⋯O motions in liquid water: Theory and experiment

Abstract

A new theory is proposed to describe spectral effects of the coupling between molecular rotations and OH¯O motions in liquid water. The correlation function approach is employed together with a special type of development in which the coupling energy of these two motions is the expansion parameter. The isotropy of the liquid medium plays an essential role in this study. Based on this theory, a new infrared pump-probe experiment is described permitting a visualization of molecular rotations at subpicosecond time scales. Full curves relating the mean squared rotational angle and time, and not only the rotational relaxation time, are measured by this experiment. However, very short times where the incident pulses overlap must be avoided in this analysis. The lifetime of OH¯O bonds in water is rotation-limited.

Strong temperature dependence of water reorientation in hydrophobic hydration shells

“…Here we study the temperature dependence of the dynamics of the hydrophobic hydration shells using polarization-resolved femtosecond midinfrared spectroscopy. [20][21][22][23][24][25][26][27][28][29][30] We observe that heating of the solution leads to a strong acceleration of the molecular reorientation of the hydrophobic hydration structures, which indicates that these structures become much more labile.…”

Four‐photon coherent spectroscopy of orientational motion of H2O molecules in liquid water

“…9,10 The rotational signatures of water molecules have been observed for water vapor in the suband supercritical states. 11 The rotationally resolved Raman spectrum of H 2 molecules dissolved in liquid water has been reported.…”

Vibrational Förster transfer to hydrated protons

“…[12][13][14][15][16][17] Previous studies on pure liquid water have shown that Förster type interactions between water molecules lead to vibrational energy transfer on a time scale Ͻ100 fs. 3,5 Similar interactions have been observed for the amide vibrations of peptides 18 and for vibrations of adsorbed molecules.…”