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Abstract:
Vibrational action spectroscopy employing infrared radiation from a freeelectron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the freeelectron laser of the Fritz Haber Institute. In this paper we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V2O3(0001) film on Au(111) as well as adsorbate vibrations demonstrating that this method is highly surface sensitive We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to sub-surface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the non-thermal channel and its insensitivity to sub-surface modes makes this technique an ideal tool for the study of surface-located vibrations Vibrational spectroscopy provides key information on surfaces and the interaction of adsorbed species with those surfaces. The most prominent examples are infrared reflection absorption spectroscopy (IRAS, for some early examples see ...[1-3]) and high-resolution electron energy loss spectroscopy (HREELS). .........[4] Both techniques exhibit considerable drawbacks In IRAS the intense instrumental contributions to the spectrum are removed via division by a reference sample spectrum, which has the consequence that an IRAS spectrum contains structures not only of the sample under consideration, but also of the reference sample, which can cause ambiguities ...
