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Title: Interfacial structures of acidic and basic aqueous solutions

Phase-sensitive sum-frequency vibrational spectroscopy was used to study water/vapor interfaces of HCl, HI, and NaOH solutions. The measured imaginary part of the surface spectral responses provided direct characterization of OH stretch vibrations and information about net polar orientations of water species contributing to different regions of the spectrum. We found clear evidence that hydronium ions prefer to emerge at interfaces. Their OH stretches contribute to the 'ice-like' band in the spectrum. Their charges create a positive surface field that tends to reorient water molecules more loosely bonded to the topmost water layer with oxygen toward the interface, and thus enhances significantly the 'liquid-like' band in the spectrum. Iodine ions in solution also like to appear at the interface and alter the positive surface field by forming a narrow double-charge layer with hydronium ions. In NaOH solution, the observed weak change of the 'liquid-like' band and disappearance of the 'ice-like' band in the spectrum indicates that OH{sup -} ions must also have excess at the interface. How they are incorporated in the interfacial water structure is however not clear.
Authors:
; ; ;
Publication Date:
OSTI Identifier:
951194
Report Number(s):
LBNL-1721E
Journal ID: ISSN 0002-7863; JACSAT; TRN: US0902157
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 130; Related Information: Journal Publication Date: 2008
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Earth Sciences Division
Country of Publication:
United States
Language:
English
Subject:
54; 58; AQUEOUS SOLUTIONS; IODINE IONS; OXONIUM IONS; OXYGEN; SPECTRAL RESPONSE; SPECTROSCOPY; WATER; WATER VAPOR