Temporary π* and σ* Anions and Dissociative Electron Attachment in Chlorobenzene and Related Molecules

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Coupled-cluster, Hartree−Fock, and B3LYP calculations are employed to study the gas-phase empty-level structures of chlorobenzene, benzyl chloride, and (2-chloroethyl)benzene. All three theoretical approaches reproduce accurately the energy trends of vertical electron attachment observed in the electron transmission spectra and predict the occurrence of the lowest σ* resonance about 2 eV higher in energy than the lowest π* resonance, in contrast with a recent suggestion by others. The relative cross sections for dissociative electron attachment are measured in the benzene derivatives and in saturated chlorohydrocarbons. The Cl- currents and a comparison of the energies of maximum production in the dissociative attachment spectra with the resonance energies located in the electron transmission spectra clearly indicate, that in the benzene derivatives, dissociation follows electron trapping into a ring π* empty orbital and subsequent intramolecular transfer to the chlorine atom, in line with the conclusions of an earlier work.