It has been postulated that the observed high- and low-density amorphous ice forms of water, HDA and LDA, can be related to two hypothesized high- and low-density liquids, HDL and LDL, through two distinct glass transitions in the ultraviscous regime. Here, I will present our experimental study of the structure and dynamics of HDA ice as it is heated up and relaxes into the low-density form. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.<br/><br/>In addition, I will present our recent investigation using ultrafast coherent X-ray diffraction to investigate the sub-100fs dynamics of water from ambient conditions down to supercooled temperatures. This novel approach utilizes the inherent capability of X-ray speckle visibility spectroscopy of an x-ray free-electron laser to measure equilibrium intermolecular dynamics with lengthscale selectivity, by measuring oxygen motion in momentum space.<br/><br/>Finally, I will discuss of future outlook and possibilities of extending such measurements to study in real-time the water salt separation upon crystallization, which can provide an valuable insight to improve desalination efficiency from a molecular perceptive.

Coherent X-rays capture water dynamics from glassy to ambient conditions

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.