The invention of optical lasers led to a revolution in the field of optics and to the creation of such fields of research as quantum optics. The reason was their unique statistical and coherence properties. The emerging, short-wavelength free-electron lasers (FELs) are sources of very bright coherent extreme-ultraviolet and X-ray radiation with pulse durations on the order of femtoseconds, and are presently considered to be laser sources at these energies. FELs are highly spatially coherent to the first-order but in spite of their name, behave statistically as chaotic sources. Here, we demonstrate experimentally, by combining Hanbury Brown and Twiss interferometry with spectral measurements that the seeded XUV FERMI FEL-2 source does indeed behave statistically as a laser. The results may be useful for quantum optics experiments and for the design and operation of next generation FEL sources.

The challenges in development of solid oxide fuel cells (SOFCs) are reducing their dimensions and increasing their efficiency and durability, which requires physicochemical characterization at micro-scales of the device components during operation conditions. Recently, the unique potential of scanning photoelectron microscopy (SPEM) has been demonstrated by in-situ studies of externally-driven SOFCs, which mimic real devices. Here we overcome the gap between model and real systems using a single-chamber Ni|YSZ|Mn SOFC, supporting a range of self-driven electrochemical reactions in variable gas environments and temperatures. The reported SPEM results, obtained during spontaneous electrochemical processes occurring in reactive gas ambient, demonstrate the chemical evolution of electrodic material, in particular the lateral distribution of the oxidation state and the induced local potential, clearly marking out the electrochemically most active micro-regions of the Ni anode.

We have studied the initial stages of the heteroepitaxy of Mg on W(110) in situ, by means of complementary microscopic and spectromicroscopic techniques. In the submonolayer coverage regime the Mg film undergoes a series of structural transitions which are clearly distinguished in the diffraction pattern. Monitoring the Mg $2p$ core-level permits the identification of the different energy shifts associated with each superstructure. During deposition of the second Mg monolayer at moderate temperatures, the growth of single atomic height stripes is observed. The Mg $2p$ core level of the first (interface) and second monolayer are remarkably separated. The density, length, and width of the stripes, stabilized by the anisotropic misfit between the W(110) and Mg(0001) lattices, can be tuned by modifying the growth parameters.