SURFACE-ACOUSTIC-WAVE RESONANCE SPECTROSCOPY (SAWRS) AS A NOVEL TECHNIQUE TO STUDY SURFACE PHENOMENA

A new method is proposed for investigating surface phenomena based on the observation of the acoustic vibration modes of surface structures at high resolution. Experimental SAWR spectra can be obtained under a narrow frequency band excitation (DELTAomega/omega approximately 10(-5) in a wide range (100 kHz-10 MHz). Application of this method to Ag(111) and Pt(100) single crystals reveals the existence of very narrow resonant acoustic vibration modes with DELTAomega/omega approximately 10(-3)-10(-4) demonstrating strong anomalies in the phonon energy distribution function of solids. The behaviour of these anomalous peaks is very sensitive to surface structure and to the presence of adsorbates.