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Title: Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.
Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
1007496
Report Number(s):
LBNL-4302E
TRN: US201106%%277
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal Physical Chemistry C
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Chemical Sciences Division; Materials Sciences Division
Country of Publication:
United States
Language:
English
Subject:
36; ADSORPTION; ATOMS; HALIDES; HUMIDITY; ION MOBILITY; IRRADIATION; SATURATION; SEGREGATION; SOLVATION; THICKNESS; THIN FILMS; WATER; X-RAY PHOTOELECTRON SPECTROSCOPY Hydration, Ion segregation, saline solution aerosol