We are interested in the theoretical description of the photoemission process in gas-phase molecules, surfaces and solids, as a tool to characterize the structure and electronic properties of matter. We mostly use multiple scattering techniques to represent the wave function of the photoemitted electrons and subsequently analyze the resulting angular distribution patterns of the photoelectrons. Close collaboration with experimental groups is necessarily maintained: In the particular case of photoelectron diffraction patterns from condensed-matter systems (surfaces and nanosized clusters, for instance), the structural properties can only be determined from an interactive combination of experimental data collection and theoretical analysis.

In gas-phase, the measurement of the angular distributions of photoelectrons emitted from free molecules fixed in space have just recently become available. Previous to this work, free-molecule studies were limited to orientationally-averaged measurements, thus limiting the information derivable from the data. The dependence of such fixed-in-space angular distributions on photon energy provides an exciting new probe of electronic structure and dynamics. Multiple scattering on non-spherical potentials has proven to be a powerful theoretical approach to describe these processes.

Non-linear effects in photoemission processes from solid surfaces are currently under study as well. A major challenge remaining in condensed matter physics is the description of excited electronic states at the same level of accuracy reached in the description of the ground state. Multiphoton processes can be key to study electronic excited states. We thus investigate contributions to the photoemission spectra of orders higher than linear in the perturbation expansion with respect to the photon intensity.