BREMSSTRAHLUNG ISOCHROMAT SPECTROSCOPY USING A MODIFIED XPS APPARATUS

The new components required for bremsstrahlung isochromat spectroscopy (BIS) in UHV (10-12 Torr range) have been developed and incorporated into an x-ray photoelectron spectrometer. They consist of a Pierce electron gun and a soft x-ray photon detector, both of which have to fulfill precise geometrical conditions imposed by the already existing monochromator. A description of the design and testing of this equipment is given. The resolution and the intensity appear to be correlated so that a compromise has to be found in order to achieve high resolution with acceptable intensity. It is demonstrated on the basis of suitable spectra that the density of unoccupied states above the Fermi level can be investigated with a resolution better than 0.43 eV.