Optical second harmonic spectroscopy of reconstructed Au(100) and (111) surfaces

We have performed optical second harmonic (SH) spectroscopy of Au(100)5×20 and Au(111)√×23 surfaces, in order to gain an insight into the formation mechanism of electronic states of reconstructed surfaces. The SH intensity spectra measured in the p-in/p-out (p-polarized input and p-polarized output) polarization configuration showed peaks near 2hω=2.4 and 2.8 eV for both the Au(100) and (111) reconstructed surfaces, while a peak at 2hω=3.2 eV was observed only for the Au(100) reconstructed surface. The SH intensity peaks near 2hω=2.8 eV are attributed to an electronic transition in the hexagonal structures at the top layers of the two surfaces