Development of a high performance soft x-ray appearance potential spectroscopy (SXAPS) system

A high performance soft x-ray appearance potential spectroscopy (SXAPS) system has been designed and built. Non-derivative spectra (without using a lock-in-amplifier) are measured at a few A incident electron currents on samples. This is about 1/1000 of typical electron currents for SXAPS measurements. A new analytical method to obtain local density of empty states is developed. SXAPS Cr 2p spectra of a Cr(110) surface have been measured by the system and density of empty states is deduced by using the method. The result is compared with x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) spectra, and a theoretical calculation. The present result indicates that local density of empty states for material surfaces can be easily deduced by the analytical method.