Charge separation reactions of doubly charged benzene ions

Photoion‐photoion coincidence spectra of benzene and benzene‐d6 photoionized by He(II) light and synchrotron radiation show the existence of six major and eight minor charge‐separation reactions of the [C6H6]2+ ion. Three main groups of ion pairs are related to [C3H3]+ + [C3H3]+, [C2H3]+ + [C4H3]+ and [CH3]+ + [C5H3]+, 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 [C6H6]2+, and subsequent hydrogen loss by the singly charged fragments.