X-ray photoelectron spectroscopy: Progress and perspectives

In this overview, I will briefly explore some of the basic concepts and observable effects in X-ray photoelectron spectroscopy, including references to some key first publications, as well as other papers in this issue that explore many of them in more detail. I will then turn to some examples of several present and promising future applications of this diverse technique. Some of the future areas explored will be the use chemical shifts, multiplet splittings, and hard X-ray excitation in the study of strongly correlated materials; photoelectron diffraction and holography for atomic structure determinations; standing wave and hard X-ray excited photoemission for probing buried interfaces and more bulk-like properties of complex materials; valence-band mapping with soft and hard X-ray excitation; and time-resolved measurements with the sample at high ambient pressures in the multi-torr regime.