Recent Progress in Spectroscopies Using Soft X-ray Free-electron Lasers

Abstract

Novel light sources have been new probes or “eyes” to develop our science and technology. Soft X-ray free-electron lasers (SXFELs) are an ultrahigh brilliant soft X-ray source with ultrashort pulse-width, ultrahigh spatial coherence, and tunability of photon energy. Various experimental techniques are designed and examined with SXFEL. In this review, we focus on soft X-ray spectroscopies, such as magneto-optical spectroscopy, photoelectron spectroscopy, and non-linear spectroscopy, that were successfully developed at SXFEL beamlines of vacuum ultraviolet 3 soft X-ray photons. These techniques allow us to track femtosecond dynamics of spins and carriers in materials element-selectively or to examine electronic states with broken inversion symmetry. The SXFEL spectroscopies have become new tools to tackle with a wide range of our scientific and technical problems.