Anisotropic Orientational Motion of Molecular Adsorbates at the Air−Water Interface

The ultrafast orientational motions of coumarin 314 (C314) adsorbed at the air/water interface were investigated by time-resolved surface second harmonic generation (TRSHG). The theory and method of using TRSHG to detect both out-of-plane and in-plane orientational motions are discussed. The interfa...

Full description

Saved in:
Bibliographic Details
Published in:The journal of physical chemistry. B 1999-04, Vol.103 (17), p.3425-3433
Main Authors: Zimdars, David, Dadap, J. I, Eisenthal, Kenneth B, Heinz, T. F
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The ultrafast orientational motions of coumarin 314 (C314) adsorbed at the air/water interface were investigated by time-resolved surface second harmonic generation (TRSHG). The theory and method of using TRSHG to detect both out-of-plane and in-plane orientational motions are discussed. The interfacial solute motions were found to be anisotropic, with differing out-of-plane and in-plane reorientation time constants. This report presents the first direct observation of in-plane orientational motion of a molecule (C314) at the air/water interface using TRSHG. The in-plane reorientation time constant is 600 ± 40 ps. The out-of-plane reorientation time constant is 350 ± 20 ps. The out-of-plane orientational motion of C314 is similar to the previous results on rhodamine 6G at the air/water interface which indicated increased interfacial friction compared with bulk aqueous solution. The surface reorientation times are 2−3 times slower than the bulk isotropic orientational diffusion time.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp984468o