Single photon double ionization of carbon diselenide ( \({\hbox {CSe}}_{2}\) ) has been investigated by means of multi-particle coincidence techniques. The interpretation of the experimental spectra is helped by post-Hartree-Fock computations at the Coupled Clusters and Multi-Reference Configuration-Interaction levels to determine the energetics and electronic state potentials of \(\hbox {CSe}_2^{2+}\) and its fragments. The lowest experimental double ionization energy of \({\hbox {CSe}}_{2}\) has been found to be 24.68 ± 0.20 eV, reflecting the \(\hbox { X} ^3\Sigma ^-_g\) ground state, and is in agreement with the theoretical vertical double ionization energy of 24.41 eV. Several fragmentation channels are reported including experimental appearance energies and kinetic energy releases in comparison to theoretical results on their characteristics. In particular, we identify several purely repulsive, Coulomb explosion fragmentation channels.
