Isochromat and SXAPS Measurements on Hafnium, Tantalum, and Tungsten

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Abstract
The density of unoccupied states in the conduction band of hafnium, tantalum, and tungsten is measured employing soft X‐ray appearance potential (SXAPS) and bremsstrahlung‐isochromat spectroscopy (BIS). The MV core levels of Hf, Ta, and W with binding energies of 1662, 1735, and 1809 eV, respectively, are used for the SXAP measurements. Since the MV spectra of these elements exhibit rather poor signal to noise ratios, a novel self‐tuning SXAP spectrometer which provides the necessary stability for the required long term measurements, is employed. Isochromat spectra are taken using the very same SXAP spectrometer with an additional aluminium absorption foil in front of the X‐ray photodetector. As described previously this setup provides a BI‐spectrometer with a monochromator energy equal to the K‐absorption energy of 1560 eV of the aluminium foil. Experimentally obtained density of state (DOS) functions from BIS and deconvoluted SXAP spectra compare favourably with each other and with theoretical calculations.