Speaker
Description
Action spectroscopy with rare gas messenger atoms is commonly used for the characterization of aggregates in the gas phase. With this method vibrational spectra of clusters are measured via detection of rare gas desorption following a vibrational excitation. We have constructed an apparatus for the application of action spectroscopy with rare gas messenger atoms to surfaces of solids.
Experiments performed for neon covered V$_2$O$_3$(0001) films on Au(111) show that this method is applicable to surfaces. Rare gas desorption by excitation of surface vibrational modes is probably a single photon process as indicated by experimental observations. In addition to this surface sensitive channel there is also a bulk sensitive channel in which absorption of laser light by a state with a high absorption cross section like a bulk polarition leads to gas desorption induced by sample warming.
Infrared absorption reflection spectroscopy (IRAS) is another commonly used method for the vibrational characterization of surfaces. Surface action spectroscopy has two advantages over this method: (1) a reference spectrum is not required for surface action spectroscopy which means that modification of features by structures in the reference spectrum does not occur and (2) the use of a messenger gas offers the possibility to cover only part of the surface which means that in this case the action spectrum exclusively stems from the covered areas.
