EXAMINATION OF THE SURFACE 2ND-HARMONIC RESPONSE FROM NOBLE-METAL SURFACES AT INFRARED WAVELENGTHS

Contributing factors to the second harmonic response from Ag(111) and Au(111) surfaces have been examined in the long wavelength limit where nonresonant conditions prevail. The rotational anisotropy in the nonlinear response is found to persist for both metals in the absence of surface resonances and to show convergent behavior in both the relative phase and intensity as the incident energy is lowered from resonant to nonresonant conditions. The phase difference between the in-plane and out-of-plane responses in the long wavelength limit can be described by linear Fresnel theory. Whereas the tensor elements corresponding to the out-of-plane response are found to dominate, the in-plane contributions are found to be non-negligible.