Hard X-ray photoelectron spectroscopy experiment at SACLA. Towards femtosecond time-resolved measurement

Hard X-ray photoelectron spectroscopy (HAXPES) is well known as one of the most powerful methods to directly study the bulk electronic structure of condensed matter. In order to extend its capability for investigating transient electronic states on time scale in the femtosecond to sub-picosecond regime, we have been developing a time-resolved HAXPES (trHAXPES) system since 2010. Recently, we have demonstrated its feasibility at the X-ray free-electron laser (XFEL) facility, SACLA. As a first major step towards applying HAXPES in the study of ultrafast materials dynamics, we report here the results of systematic studies which quantify the dynamics of vacuum space-charge effects on core-level photoelectron spectra of various materials. (author)