Surface and bulk crystallization of amorphous solid water films: Confirmation of top-down crystallization

SURFACE SCIENCE

卷:652

Article

Yuan, Chunqing¹  Smith, R. Scott¹  Kay, Bruce D.¹ 

[1] Pacific Northwest Natl Lab, Div Phys Sci, Richland, WA 99352 USA

关键词: Amorphous solid water;    Crystallization kinetics;    Surface nucleation;    Temperature-programmed desorption (TPD);    Reflection absorption infrared spectroscopy (RAIRS);   

DOI  :  10.1016/j.susc.2015.12.037

来源: Elsevier

【 摘 要 】

The crystallization kinetics of nanoscale amorphous solid water (ASW) films are investigated using temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). TPD measurements are used to probe surface crystallization and RAIRS measurements are used to probe bulk crystallization. Isothermal TPD results show that surface crystallization is independent of the film thickness (from 100 to 1000 ML). Conversely, the RAIRS measurements show that the bulk crystallization time increases linearly with increasing film thickness. These results suggest that nucleation and crystallization begin at the ASW/vacuum interface and then the crystallization growth front propagates linearly into the bulk. This mechanism was confirmed by selective placement of an isotopic layer (5% D2O in H2O) at various positions in an ASW (H2O) film. In this case, the closer the isotopic layer was to the vacuum interface, the earlier the isotopic layer crystallized. These experiments provide direct evidence to confirm that ASW crystallization in vacuum proceeds by a top-down crystallization mechanism. (C) 2016 Published by Elsevier B.V.

【 授权许可】

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