Kei Kuramoto

Theoretical fine spectroscopy with symmetry adapted cluster-configuration interaction general-R method: first-row K-shell ionizations and their satellites.

Molecular core ionization spectra and their satellites were studied by the symmetry adapted cluster-configuration interaction (SAC-CI) general-R method. The core-electron binding energies of C, N, O, and F atoms of 22 molecules were calculated with an average deviation of 0.11 eV from the experimental values. The energy splittings between K-shell gerade and ungerade states were calculated and discussed in relation to the bond length. The satellite spectra of the C 1s and N 1s core ionizations of methane and ammonia were investigated. The SAC-CI general-R method gave many shake-up states with moderate intensities, reproducing the general feature of the experimental spectra, and thus enabling the detailed understanding and assignments of the core-electron ionization spectra.

C1s and O1s photoelectron satellite spectra of CO with symmetry-dependent vibrational excitations

The photoelectron shake-up satellite spectra that accompany the C1s and O1s main lines of carbon monoxide have been studied by a combination of high-resolution x-ray photoelectron spectroscopy and accurate ab initio calculations. The symmetry-adapted cluster-expansion configuration-interaction general-R method satisfactorily reproduces the satellite spectra over a wide energy region, and the quantitative assignments are proposed for the 16 and 12 satellite bands for C1s and O1s spectra, respectively. Satellite peaks above the pi(-1)pi(*) transitions are mainly assigned to the Rydberg excitations accompanying the inner-shell ionization. Many shake-up states, which interact strongly with three-electron processes such as pi(-2)pi(*2) and n(-2)pi(*2), are calculated in the low-energy region, while the continuous Rydberg excitations are obtained with small intensities in the higher-energy region. The vibrational structures of low-lying shake-up states have been examined for both C1s and O1s ionizations. The vibrational structures appear in the low-lying C1s satellite states, and the symmetry-dependent angular distributions for the satellite emission have enabled the Sigma and Pi symmetries to be resolved. On the other hand, the potential curves of the low-lying O1s shake-up states are predicted to be weakly bound or repulsive.

Theoretical Surface Spectroscopy of NO on the Pt(111) Surface with the DAM (Dipped Adcluster Model) and the SAC-CI (Symmetry-Adapted-Cluster Configuration-Interaction) Method.

Theoretical surface spectroscopy for NO on the Pt(111) surface is carried out and combined with the experimentally known facts to elucidate the structures, absorption sites, absorption energies and K-shell binding energies of NO adsorbates on the surface. The electronic structures were studied by using the dipped adcluster model (DAM) for chemisorptions on a metal surface proposed previously and the symmetry-adapted-cluster configuration-interaction (SAC-CI) method, which is an established method for studying molecular spectroscopy. The natures of the two different adsorption species suggested experimentally have clearly been identified based on the studies on the geometries, vibrational frequencies, adsorption energies, and the N and O K-shell binding energies. The PES (potential energy surface) of NO on the metal surface was also calculated. The most stable adsorption species was on the fcc or the hcp hollow site, and the on-top one was less stable. The 2-fold bridge site did not have a minimum on the PES and therefore was only transient. The inter NO interactions at higher densities were shown to be rather weak. We examined the cluster model (CM) vs the DAM as a model of the surface adsorption on a metal surface. The CM was shown to be unable to describe the adsorption of NO on a metal surface, demonstrating the importance of the electron transfer between the NO and Pt surfaces included in the DAM. The DAM and the SAC-CI methods proved to be a useful tool for studying the nature, electronic structure, and the spectroscopic properties of the adsorbates on a metal surface.