“…This solid–light interaction provides information about phases, composition etc., which is why XPS is a promising tool to determine the physical properties of a material. [ 139 ] In addition to providing information about elemental composition of the material surface and binding states of the constituting elements, X‐ray photoelectron spectroscopy (XPS) proves to be an extraordinary technique for characterization of plasmonic properties as well. The collective oscillations of conduction electrons (plasmons) in free‐electron like metals such as Be, Na, Mg, Al, which only contain s and p orbitals, is highly noticeable.…”