Recoil effects in molecular photoemission

A departing photoelectron leaves the molecular ion with a recoil momentum that is distributed between translational motion and the excitation of vibrational and rotational energy levels. In this review, recent measurements of recoil induced effects in core- and valence level photoelectron spectra of free molecules are summarized. The experimental examples are preceded by the outline of a semiclassical model to treat the recoil effects in free molecules.