  We have investigated the electronic structures of newly discovered
superconductor FeSe1-x by bulk-sensitive photoemission spectroscopy (PES). The
large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF)
and it decreases steeply toward EF . Compared with results of band structure
calculations, narrowing the Fe 3d band width and the energy shift of the band
toward EF are found, suggesting a mass enhancement due to the weak electron
correlation effect. Meanwhile, Fe 2p core-level PES reveals a strong itinerant
character of Fe 3d electrons. These features are very similar to those in other
Fe-based high-Tc superconductors.
