Surface analysis using time-resolved techniques in extreme-ultraviolet free-electron-laser radiation

When a short pulse of high-intensity free-electron-laser (FEL) radiation strikes a surface, the resulting electronic excitations may stimulate the emission or ejection of any of several particles: ionic or neutral atomic or molecular particles, electrons, or photons. Using high-speed pulse-timing techniques, a variety of information may be obtained. It is possible to determine the kinetic-energy spectra of massive particles; to identify massive particles via their charge-to-mass ratios or via their laser-induced fluorescence; and to determine the angular distributions and coincidences of emitted particles. From such information (and its spectral dependence), details of the surface structure and the emission process can be learned. Examples relevant to semiconductor surface studies are discussed