Core Level Photelectron and X-Ray Absorption Spectroscopy of Free Argon Clusters: Size-Dependent Energy Shifts and Determination of Surface Atom Coordination

Core level photoelectron and x-ray absorption spectra for free argon clusters from 〈N〉≈5 to 〈N〉≈4000 are presented. Spectral features originating from surface and bulk sites of the clusters are identified. These are seen to shift with cluster size. From the development of the spectra from the isolated atom to the largest clusters, information about both the size-dependent cluster-specific electronic structure and that of the “infinite” solid is obtained. Using a simple model for the core level binding energy shifts, effective surface coordination numbers are derived. These range from 5.3 for 〈N〉≈10 to 8.5 for the solid

Core level binding energy shifts and polarization screening: A combined experimental and theoretical study of argon clusters

Photoelectron spectra of the argon 2p core level for free argon clusters of up to 4000 atoms are compared to detailed calculations. The comparison shows that the size‐dependent shifts of the core level binding energy can be explained in a pure polarization‐screening model. Important differences arise between the shifts for the bulk (interior) and the surface atoms. The agreement between experiment and theory allows the extrapolation of the cluster data to the ‘‘infinite’’ solid. In this way we obtain the shifts of the core level binding energy between the free atom, the surface atom and the bulk of argon. The relation between these shifts and those of the first ionization potential is discussed

Valence- and inner-shell spectroscopy on rare-gas clusters

An overview of the present status of valence- and inner-shell spectroscopy on rare-gas clusters is given. Fluorescence excitation, time-of-flight ion and photoelectron spectroscopy with synchrotron excitation was used to study the electronic level structure of rare-gas clusters. Ne and Ar clusters covering the size range from the monomer up to a few thousand atoms/cluster are used as examples. Specific advantages and limitations of different methods of the study of electronic level structure as well as geometrical structure are discussed. A wealth of information on the evolution of electronic level structure has already been obtained. Nevertheless, several interesting questions concerning the evolution of energy-level shifts remain unresolved. Prospects for future work and experimental developments are given

Performance of the extreme ultraviolet high resolution undulator beamline BW3 at Hasylab: First results and time‐of‐flight spectroscopy

The extreme ultraviolet beamline BW3 at Hasylab is a state of the art beamline for the energy range 15–2000 eV consisting of a triple undulator equipped with a modified high‐flux SX‐700 plane grating monochromator. The first three optical elements of the beamline are made of graphite coated with SiC to withstand the high heat load at the 4.5 GeV storage ring Doris III. Excellent spectral resolution of the order of 104 at the nitrogen K edge at 400 eV is obtained by replacing the elliptical focusing mirror of the original SX‐700 design by a spherical mirror with very small tangent errors and with a large focal length in order to suppress spherical aberrations. In the energy range 50–1700 eV a photon flux of 1011–1013/s is obtained in a bandpass of 0.1%. Photoionization and photoemission measurements on atoms, molecules, and clusters making use of time‐of‐flight techniques demonstrate the excellent performance of the beamline