Characterisation of the VG ESCALAB instrumental broadening functions by XPS measurements at the Fermi edge of silver

A mathematical algorithm is presented to determine the broadening function of an XPS spectrometer using smoothed first derivatives of experimental Fermi edges for the VG ESCALAB 220i-XL instrument at various pass energies. Different smoothing algorithms were applied and optimal parameter sets are discussed, as this has not been done before. The smallest error in the determination of the broadening function occurred with the usage of spline functions. It is shown that the broadening function of the spectrometer can be well described by a symmetrical Gaussian function. The resolution and the intensity dependence on the pass energy is determined for the spectrometer, as well as the linewidth of the monochromated X-rays.