Photodetachment photoelectron spectroscopy of perylene and CS2: two extreme cases

Photodetachment photoelectron spectroscopy has been applied to the investigation of mass selected and supersonic jet cooled perylene and CS2 anions, used as model systems for large and small molecules. For perylene, the adiabatic electron affinity is determined to be 973 ± 5 meV. In contrast, despite a resolved bending mode progression in the neutral ground state, only an upper limit of 800 meV can be given for the adiabatic electron affinity of CS2. This is due to poor Franck-Condon overlap between the bent anionic and the linear neutral molecular structures. The vibrational intensity distributions in the spectra of CS2 and perylene can be taken as prototypes for small and large molecules: the different effects of the surplus electron in either a localized or delocalized π∗ orbital on geometry can be generalized. The spectra are the first anion photodetachment photoelectron spectra of these molecules.