Photo-double-ionization mechanisms in aromatic hydrocarbons

We have measured the ratios of doubly to singly charged molecular parent ions of benzene (partially deuterated), naphthalene, anthracene, pentacene, pyrrole, furan, selenophene, and coronene for photon energies ranging from threshold to the carbon K shell. The photon-energy dependence of the ratio curves has been analyzed and compared to each other for the above molecules. We conclude that two-and in some cases three-different photo-double-ionization mechanisms exist for aromatic hydrocarbons. One of the mechanisms is the formation of a two-electron pseudoparticle. This finding may be useful in the quest for understanding high-temperature superconductivity.