Vibrational structure in inner shell photoionization of molecules

The sudden removal of an inner shell electron from a molecule by photoionization generally leads to the production of vibrationally excited cationic states. Recent experimental results on this phenomenon, most of them obtained on third generation synchrotron radiation sources, are reviewed. Most of the examples that will be discussed involve small molecules with second row constituent atoms, such as C, N and O. In detail, the inner shell photoelectron spectra of CH 4 , CO, N 2 , O 2 , CO 2 , ethane, furan and benzene will be discussed. Emphasis will be placed on the coupling of the vibrational with the electronic structure in the case of degenerate or nearly degenerate electronic final states.