Complementary vibrational and reflectance anisotropy spectroscopic determination of molecular azimuthal orientation

Azimuthal orientations of 9-anthracene carboxylate (9-AC) on clean and p(2 x 1)O/Cu(110) surfaces were determined from a reflectance anisotropy spectr oscopy (RAS) signal derived from an intramolecular electronic transition, T he magnitude of the molecular signal on the p(2 x 1)O/Cu(110) surface is 4- 5 times larger than on the clean surface, We present a complete vibrational assignment of adsorbed 9-AC based on Fourier transform infrared and on- an d off-specular high resolution electron energy loss spectroscopy (HREELS) a nd ab initio calculations. Correlation of the off-specular HREELS on p(2 x 1)O/Cu(110) with the RAS results demonstrates that the magnitude of the RAS signal depends on the degree of azimuthal orientation. (C) 1999 Elsevier S cience B.V. All rights reserved.