Angle-resolved photoelectron spectroscopy of size-selected clusters using synchrotron radiation

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During the first funding period a new method for photoelectron spectroscopy of mass-selected clusters and nanoparticles has been developed and will now be used for measurements. Clusters need to be size-selected prior to an experiment and for this the particles must be charged. Usually, the low target density in an ion beam is compensated by the high intensity of a laser. The maximum photon energy provided by commercial lasers is 7.9 eV restricting this type of experiments to the study of the uppermost occupied orbitals. In contrast, with synchrotron radiation the complete valence bands und even core levels of size-selected clusters could be studied. The problem is the low intensity of synchrotron radiation. During the first funding period, we demonstrated that it is possible to record valence band photoelectron spectra of size selected cluster ions with synchrotron radiation. After this first success, we modified and improved the machine further. At a light intensity of 10**13 photon/s it is now possible to record angle-resolved photoelectron spectra within 10-30 min. Now, the new technique will be used to study the chemisorption of O2, CO and N2 on metal clusters.