STATUS AND PERSPECTIVES OF HIGH-RESOLUTION SPECTROSCOPY IN THE SOFT-X-RAY RANGE

The present status in high-resolution photoabsorption and photoemission spectroscopy using synchrotron radiation in the soft x-ray range (40 eV less-than-or-equal-to h-nu less-than-or-equal-to 1000 eV) is described. With the SX700/II monochromator, operated by the Freie Universitat Berlin at the Berliner Elektronenspeicherring fur Synchrotronstrahlung (BESSY), a resolving power of up to greater-than-or-equal-to 10 000 has been achieved. A practical feature of this monochromator is given by the fact that excellent energy resolution is achieved with a single 1221-lines/mm grating in the whole soft x-ray range considered. This opens up new opportunities in core-level photoabsorption spectroscopy of atoms, molecules, adsorbed species, and solids. A combination of the SX700/II beam line with a high-resolution electron spectrometer (DELTA-E congruent-to 15 meV) enables resonant photoemission studies of rare-earth materials in the 4d --> 4f giant-resonance region with unprecedented resolution and also at the 3d --> 4f absorption thresholds. This spectroscopic progress provides new insight into the correlated electronic structure of Ce systems.