Double-core ionization photoelectronspectroscopy of C6H6: Breakdownof the “intuitive”ortho-meta-parabinding energy ordering of K−1K−1states

Single-site Double-Core Hole (ss-DCH or K −2) and two-site Double-Core Hole (ts-DCH or K −1 K −1) photoelectron spectra including satellite lines were experimentally recorded for the aromatic C 6 H 6 molecule using the synchrotron radiation and multielectron coincidence technique. Density functional theory and post-Hartree-Fock simulations providing binding energies and relative intensities allow us to clearly assign the main K −2 line and its satellites. K −1 K −1 states' positions and assignments are further identified using a core-equivalent model. We predict that, contrary to what has been observed in the C 2 H 2n series of molecules, the K −1 K −1 energy-level ordering in C 6 H 6 does not reflect the core-hole distances between the two holes.