Accession Number:

ADA379636

Title:

Surface Structural Studies of Methane Sulfonic Acid at Air/Aqueous Solution Interfaces using Vibrational Sum Frequency Spectroscopy

Descriptive Note:

Technical rept. 1 Jun 1999-31 May 2000

Corporate Author:

OREGON UNIV EUGENE DEPT OF CHEMISTRY

Personal Author(s):

• Allen, H. C.
• Raymond, E. A.
• Richmond, G. L.

Report Date:

2000-07-10

Pagination or Media Count:

28.0

Abstract:

Atmospheric gas phase species such as methane sulfonic acid MSA are adsorbed and accommodated into atmospheric aqueous-phase aerosols and in some cases MSA is thought to be produced via aerosol surface chemistry. The studies described herein probe the surface molecular structure of MSA at aqueous solution surfaces using surface vibrational sum frequency spectroscopy VSFS. In the studies presented here, it is shown that MSA partitions at the surface and that the surface MSA has a preferred surface orientation in which the MSA methyl group points away from the liquid surface. The surrounding surface water structure is significantly affected by the adsorption of MSA. Small amounts of MSA at the surface of water enhances the intermolecular hydrogen bonding between interfacial water molecules. Additional VSF studies show that MSA is effectively displaced by sulfuric acid at an aqueous surface. The structural details presented here may have implications for understanding atmospheric aerosol growth properties.

Descriptors:

• *AEROSOLS
• *CLIMATE
• *ATMOSPHERIC CHEMISTRY
• ADSORPTION
• MOLECULAR STRUCTURE
• AIR WATER INTERACTIONS
• SULFURIC ACID
• SULFONIC ACIDS

Subject Categories:

• Meteorology
• Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE