Masahide Ohno

Many‐body calculation of the valence photoemission spectrum of Fe(CO)5

The valence photoemission spectrum of Fe(CO)5 is calculated by the ADC(3) Green’s function method. The overall agreement with the experiment is good. It is shown that the quasiparticle picture (QPP) for the outer and inner valence levels (except the 8a‘2 level) derived primarily from CO ligand orbitals breaks down completely due to the one‐hole/two‐hole–one‐particle (1h/2h1p) charge transfer (CT) coupling in the bonded system. Compared to Ni(CO)4 the many‐electron effect is much stronger in Fe(CO)5. In Cr(CO)6 and Fe(CO)5 the 3d shell is incompletely filled, but in contrast to Cr(CO)6 in Fe(CO)5 there is no significant contribution from the local metal excitations. It is shown that for the 8a■2 level the 1h state is still more stable than the 2h1p states. Consequently the main line (with an intensity of 0.76) is interpreted as the 1h state where the screening charge resides on the bonding orbital which is more polarized toward the ligand than in the ground state. The satellites are dominated by 2h1p confi...

Decay of the resonantly excited states of atomic Xe

Abstract The 4p−1 → 6s1 resonant excitation energy and decay width of the Xe atom are calculated by an ab initio Greens function method. The dipolar relaxation energy shift of the 4p 3 2 −1 → 6s1 resonantly excited state of the Xe atom is due mainly to the 4p 3 2 −16s1 → 4d−26s1 ϵf super-Coster-Kronig (sCK) spectator decay process. The calculated excitation energies are overestimated by 1.0 eV. For the 4p 1 2 −1 → 6s1 resonant excitation, the quasi-particle picture of the resonant excitation breaks down completely because of the 4p 1 2 −16s1 → 4d−26s1 ϵf sCK spectator decay process.

Anomalous Auger decay in adsorbates

Abstract In the backbonding energy region of adsorbate Auger spectra, the deexcitation processes involving the screening electron, can lead to a one-hole-like final state instead of a two-hole final state. The “negative” U invoked for the two-hole final state of CO adsorbed systems is explained in terms of the presence of the one-hole-like final state. The relaxation of the resonantly core level excited neutral state to the core level ionized state by the “shakedown” of the resonantly excited electron to the ligand character screening orbital (instead of delocalization of the electron to the empty substrate band) leads to the participant decay of the bonding level close to the Fermi level.

Core hole screening mechanism of adsorbates

Abstract The concept of the cooperative core hole screening mechanism is discussed in detail by using a cluster configuration interaction (CI) approach. The XPS core hole spectral features of adsorbate/substrate systems such as CO Ni and N 2 Ni depend on the local metal s-d population of the substrate metal atom. The spectral features of the coadsorbed systems such as CO/H/Ni and of N2 adsorbed on a Ni alloy surface are different from those of CO Ni and N 2 Ni , respectively. These spectral feature changes are explained by the cooperative core hole screening mechanism. The absence of the shake-up satellite in the XAS spectrum is also explained in the same manner.

Theoretical study of the valence-level photoemission spectrum of C6H6 adsorbed on Ni, Pd,and Pt metal surfaces

The valence hole spectral functions of the NiC6H6, PdC6H6, and PtC6H6 model molecules are calculated by the ab initio third-order algebraic-diagrammatic-construction [ADC(3)] Green-function method using an extended basis set. The calculation was performed assuming top-site adsorption. The theoretical predictions are compared with the experimental angle-resolved valence-level photoemission spectra of C6H6 adsorbed on Ni(110) Pd(110), Pd(111), and Pt(111) surfaces. The calculations provide an overall good agreement with experiment, and confirm the previous experimentally determined assignment of the spectra. A comparison with the results for the free C6H6 molecule shows that the many-body effects are considerably enhanced by the presence of the metal atom. There is a strong splitting of the lines and a concomitant intensity redistribution caused by the metal-ligand π-π* charge-transfer excitations. The ordering of the ionization levels of the adsorbate is the same as the one of the free molecule. For C6H6 on a Ni(110) surface the presence of the metal-ligand π-π* charge-transfer satellite of non-negligible spectral intensity accompanying the 1b2 ionization process is predicted about 10 eV below the Fermi level, which has not been observed so far. The influence of the bending of the H atoms out of the hexagonal ring plane on the photoemission spectrum is small.

Theoretical study of the valence level photoemission spectrum of C2H2 adsorbed on a Ni metal surface

In order to investigate the valence-level photoemission spectrum of C2 H4 adsorbed on a Ni metal surface, we calculated the valence-hole spectral functions of NiC2 H4 (π bonding) using the ab initio third-order algebraic-diagrammatic-construction (ADC(3)) Green-function method using an extended basis set. We obtained an overall good agreement with experiment. The changes in the spectral features such as the changes in the separations of the ionization energies from the gas phase to the chemisorbed phase are due to the metal ligand bonding exerted via the charge-transfer excitations and do not arise from the distortion of the molecule, which occurs upon chemisorption.

Theoretical and experimental studies of the valence photoemission spectrum of propionitrile

Abstract The valence photoemission spectrum of propionitrile for all outer and inner valence levels up to the ionization energy of 23 eV is calculated by ab initio third-order algebraic diagrammatic construction (ADC(3)) Greens function method. The spectrum is also measured by high resolution He I photoelectron spectroscopy to resolve additional spectral features mainly due to the vibronic excitations. The present (ADC(3)) calculation provides a fairly good description of the vertical-electronic ionization spectral features of the valence PES spectrum of propionitrile. From the ionization threshold up to and including the 8a′ ionization, the ionization phenomena appear essentially as one-particle processes. For 11a′ and 10a′ ionization, the hole mixing occurs between this pair of ionization of the same symmetry, although the hole mixing is not so significant as in molecules containing several CN groups. For the innermost 7a′ band, the breakdown of the one-electron picture occurs.

MANY-ELECTRON EFFECTS IN THE VALENCE PHOTOEMISSION SPECTRUM OF 1,3,5,7-CYCLOOCTATETRAENE

Abstract The valence photoemission spectrum of 1,3,5,7-cyclooctatetraene (COT) has been calculated by an ab initio third order algebraic diagrammatic construction (ADC(3)) Greens function method and also measured by high resolution He I photoelectron spectroscopy. The major spectral features are well reproduced by the present many-body calculation. The additional spectral features observed at 10.054 and 12.757 eV cannot be predicted by either the ADC(3) or previous CI calculations, and are assigned to a Jahn-Teller distortion.

High resolution He I photoelectron spectrum of cyanocyclopropane

Abstract The He I photoelectron spectrum of cyanocyclopropane has been revisited both experimentally, under high resolution and high sensitivity, and theoretically by ab initio third-order algebraic diagrammattic construction (ADC(3)) Green unction calculations. The agreement between theory and experiment is excellent.