Paper SS-WeM10
Surface and Bulk Crystallization Kinetics of Amorphous Solid Water Nanoscale Films

Wednesday, October 21, 2015, 11:00 am, Room 112

We investigate the crystallization kinetics of nanoscale amorphous solid water (ASW) films using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). ASW is a metastable form of water created by vapor deposition on a cold substrate (T < 130 K). In prior work, we reported the episodic release of trapped gases in concert with the crystallization of ASW, a phenomenon that we termed the “molecular volcano.” The observed abrupt desorption is due to the formation of cracks that span the film to form a connected pathway for release. In a recent study we used the selective placement of an inert gas layer is used to show that cracks form near the top of the film and propagate downward into the film. Those experiments showed that, after some induction time, cracks propagate linearly in time with an Arrhenius dependent velocity consistent with the crystallization growth rates reported by others. This suggested a direct connection between the crystallization growth and the crack propagation rate. In the present study we directly measure the surface (using TPD) and bulk (using RAIRS) ASW crystallization kinetics as a function of film thickness. These results show that nucleation and crystallization begins at the ASW/vacuum interface and then the crystallization growth front propagates linearly into the bulk. The details of the experiment and the interpretation of the results will be discussed in detail.

This work was supported by the US Department of Energy, Office of Science (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. The research was performed using EMSL, a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by Battelle operated for the DOE.