SPring-8, the large synchrotron radiation facility

Date&Time: 13:30-15:00, 30 Jan 2004

Speaker: Prof. Cristof Kunz
Affiliation: Physikalisches Institut, University of Hamburg

Abstract
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Photoemission spectroscopy at high energies provides a means to better probe electron states in the bulk beyond the surface and to combine the method with diffraction techniques. We present here first results in the valence band region with hard X-rays in the energy range 5 - 14.5 keV. Au, YBCO and graphite samples were used to demonstrate the feasibility of this spectroscopy at the undulator beam-line ID32 of the ESRF. The resolution obtained was better than 200meV. The count rate was sufficient to allow even higher resolution had not the stability of the power supplies set the limit. A specially designed high-voltage retarding lens preceding a commercial Perkin Elmer PHI 10-360 electron analyzer was used. The cross sections for sub-shell excitations in the region of low binding energy were determined on an absolute scale. They are higher than the theoretical atomic cross sections calculated by Scofield for Au by a factor 2 to 8 depending on the energies and the specific sub-levels. The results provide a basis for the planning of experiments in this energy range and for estimating the expected count rates of new instrumentation. In addition measured cross sections provide input to refine theoretical models.
Work performed together with:
S. Thiess, B.Cowie, T.-L. Lee, M. Renier and J. Zegenhagen
ESRF, F-38043 Grenoble CEDEX