Excited and ionized states of RuO4 and OsO4 studied by SAC and SAC-CI theories

The excitation and ionization spectra of RuO₄ and OsO₄ are studied theoretically by the symmetry-adapted cluster (SAC ) and SAC-CI theories. This is the attempt to assign whole of the spectra by ab initio calculations including electron correlations. In the ground state, electron correlations work to reduce the polarity of the M–O bond overestimated in the Hartree–Fock calculation. The Os–O bond is stronger than is the Ru–O bond, which is reflected in the differences of the excitation and ionization spectra of RuO₄ and OsO₄. The excitation energies of the experimental spectra are well reproduced by the SAC-CI theory, though the calculated intensities of some peaks are very small in comparison with the experiments. The outer-valence ionization spectra calculated by the SAC-CI theory agree well with the experimental photoelectron spectra. Some shake-up peaks that are accompanied with an electron-transfers from oxygen to metal are also calculated.