Charge separation reactions of doubly charged benzene ions

Photoion‐photoion coincidence spectra of benzene and benzene‐ d 6 photoionized by He(II) light and synchrotron radiation show the existence of six major and eight minor charge‐separation reactions of the [C 6 H 6 ] 2+ ion. Three main groups of ion pairs are related to [C 3 H 3 ] + + [C 3 H 3 ] + , [C 2 H 3 ] + + [C 4 H 3 ] + and [CH 3 ] + + [C 5 H 3 ] + , with appearance energies of 32.2 ± 0.5 eV, 31.3 ± 0.5 eV and 28.4 ± 0.3 eV. The kinetic energy release is the same for all pairs within a group, irrespective of hydrogen number, but differs from group to group. Results are interpreted in terms of fast, direct charge separation of [C 6 H 6 ] 2+ , and subsequent hydrogen loss by the singly charged fragments.