Surface raman spectroscopy of trans-stilbene on Ag/Ge(111): surface-induced effects
Journal
Journal of Physical Chemistry C
Journal Volume
113
Journal Issue
1
Pages
208-212
Date Issued
2009
Author(s)
Abstract
The vibrational features of self-organized submonolayer trans-stilbene on the Ag/Ge(111)−(√3 × √3)R30° surface have been investigated by Raman spectroscopy in ultrahigh vacuum at 100 K. A red shift in the C═C stretching mode of the olefinic group at 1625 cm−1 and enhanced Raman activity of the peak at 1568 cm−1 were observed, as compared with those corresponding to a multilayer trans-stilbene. Electronic interaction between trans-stilbene and the underneath surface and Raman spectra were calculated based on density functional theory. The calculated Raman spectra are in good agreement with the experimental results, supporting the calculated molecular geometry of the adsorbed trans-stilbene, which exhibits a predominant bond elongation in the olefinic group and a torsional angle between the phenyl ring and the olefinic plane. Analysis of the partial density of states shows that the lowest unoccupied molecular orbital is broadened and lowered to cross the surface Fermi level by the interaction with the surface, facilitating surface charge transfer and thus destabilizing the C═C double bond.
Publisher
American Chemical Society
Type
journal article