Hydrogen bonding in glassy liquid water from Raman spectroscopic studies

Abstract

In order to investigate subtle differences in the local structure and bonding of amorphous ices, glassy liquid water was produced by rapid cooling of micrometer sized water droplets. Samples were first studied with power x-ray diffraction (PXRD) and differential scanning calorimetry (DSC) to ensure that the production technique resulted in amorphous material with low crystalline content. Solutions containing 5% D2O in H2O and 5% H2O in D2O were vitrified, cooled to 12 K, and used to collect Raman spectra of the decoupled O–D (ΔνOD=2440 cm−1) and O–H (ΔνOH=3302 cm−1) vibrations, respectively. Samples were then annealed from 90 to 180 K in temperature intervals of 10 K. During each annealing step the samples were held isothermally for 15 min before rapidly cooling them back down to 12 K for data collection. The transition from amorphous to crystalline material was observed to occur between 150 and 160 K. Raman frequency shift data were then used to estimate the distribution in the hydrogen-bonded O–H––O distances using known correlations. The local bond strengths and O–H––O distances in vitrified liquid water were found to be very similar to those in vapor-deposited amorphous water.