Doubly ionized states of hexafluorobenzene studied by high-resolution Auger electron and double-charge-transfer spectroscopies

Double-charge-transfer (DCT) spectroscopy has been used to measure the double-ionization energies of C₆F₆. OH⁺ and F⁺ projectile ions with translational energy of 6 keV, which tend to populate triplet states in the dication, were used. From the position of peaks in the resultant DCT spectra, C₆F₆ double ionization energies of 26.3 ± 0.5, 28.4 ± 0.5, 29.2 ± 0.5, 32.2 ± 0.5, 35.0 ± 1 and 40.0 ± 1 eV were determined. The photon-induced Auger electron spectra of C₆F₆ were recorded. The Auger electron spectra are dominated by transitions to final states of singlet symmetry. Ten distinct structures are observed in the C 1s Auger electron spectrum centred at double ionization energies of 26.63 ± 0.1, 30.37 ± 0.1, 34.68 ± 0.1, 36.26 ± 0.1, 37.84 ± 0.1, 39.19 ± 0.2, 42.73 ± 0.3, 46.51 ± 0.1, 49.20 ± 0.1 and 50.40 ± 0.2 eV. Five structures were observed in the F 1s outer-outer spectrum, centred at double ionization energies of 42.20 ± 0.1, 46.14 ± 0.1, 48.61 ± 0.1, 52.53 ± 0.1 and 56.9 ± 0.1. Additional structures are observed in the outer-inner and inner-inner spectrum. A comparison has been made between the results from the present work and those obtained in a recent coincidence study (K. Ibrahim, P. Lablanquie, M-J. Hubin-Franskin, J. Delwiche, M. Furan, I. Nenner, D. Hagan and J. H. D. Eland, J. Chem. Phys., 1992, 96, 1981). Green's function calculations have been performed to assist the interpretation of the spectra.