title: Valence ionization spectra of group six metal hexacarbonyls studied by the symmetry-adapted cluster-configuration interaction method.
abstract: The valence ionization spectra up to 20 eV of group six metal carbonyls, chromium hexacarbonyl, molybdenum hexacarbonyl, and tungsten hexacarbonyl were studied by the symmetry-adapted cluster-configuration interaction (SAC-CI) method. The assignments of the spectra are given based on reliable SAC-CI calculations. The relativistic effects including the spin-orbit effects are important for the ionization spectrum of W(CO)(6). The relation between the metal-CO distance and ionization energies was examined. The lowest ionization energies of the three metal carbonyls are approximately the same because of the energy dependence of the metal-CO length and relativistic effects. In Cr(CO)(6), the Cr-CO interaction significantly increases the lowest ionization energy in comparison with Mo(CO)(6) and W(CO)(6) because of the relatively short metal-CO bond length. The relativistic effect reduces the lowest ionization energy of W(CO)(6) because the effective core potential of 5d electrons is more efficiently screened as a result of the relativistic contraction of the inner electrons.
authors.affiliation: Quantum Chemistry Research Institute, JST CREST, Kyodai Katsura Venture Plaza, North building, 36-1 Goryo Oohara, Nishikyo-ku, Kyoto 615-8245, Japan. fukuda@qcri.or.jp
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Fukuda
authors.forename: Seigo
authors.initials: S
authors.lastname: Hayaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakatsuji