“…X-rays were supplied by an undulator beam line of Photon Factory (KEK-PF): BL-2A. The BL-2A beam line is dedicated to a soft X-ray region ranging from 1700 eV to 5000 eV using a Ge(1 1 1) double crystal monochromator [30]. The X-rays hit the sample at the incidence angle of 70°and the photon flux was estimated as 10 11 photons/nm 2 /s.…”