Ground, excited and ionic states of unstable molecules

New coincidence techniques in photoelectron spectroscopy of molecules and clusters made it possible to approach complete experiments in molecular photoionization for the first time. This method -angle-resolved photoelectron-photoion coincidence spectroscopy -a versatile tool for the study of electron-ion momentum vector correlations reveals the intermolecular scattering and associated interference of the photoelectron on its way out. This effect is illustrated by selected showcase examples of molecular core level and valence photoionization. The application of this `photoelectron interferenceʹ concept on the valence photoionization of fullerenes, in particular C60, is discussed.