Development of Fluorescence-yield Wavelength-dispersive Soft X-ray Absorption Spectroscopy for Real-time Observation of Surface Chemical Reaction

A novel X-ray absorption spectroscopy technique in the soft X-ray region has been developed, which enables the real-time observation of surface chemical reactions under near ambient pressures by sequentially recording the absorption spectra without scanning the photon energy of the incident X-rays. The wavelength-dispersed soft X-rays, in which the wave-length (energy) continuously changes as a function of position, illuminate the sample, and the fluorescence soft X-rays emitted at different position on the sample are separately corrected by an imaging optics consisting of two spherical mirrors. By using the developed system, a series of X-ray absorption spectra was recorded during the oxidation reaction of copper surface under air pressure of up to 5000 Pa at a data acquisition time of 10 s for each spectrum. The curve-fitting analysis for the recorded spectra indicates that only the CuO species increases with 500 Pa air, while Cu2O appears at 5000 Pa.