On the interpretation of valence band photoemission spectra of NiO

The valence band photoemission spectrum and the L₃VV Auger spectrum of NiO are compared. The satellite found in the valence band of NiO and other Ni compounds is interpreted as an unscreened 3d⁷ final state, whereas the main d-emission is a 3d⁷ final state screened by a d electron in an exitonic state.     

Strength of plasmon satellites in the valence band photoemission spectra of metals

The strength of the first bulk plasmon satellite in the valence band photo-emission spectra of simple metals has been calculated for the dispersionless plasmon model. It is found that due to the mobility of the final state hole in the valence band, the strength of the plasmon satellite is lowered compared to that of the core state. This conclusion is qualitatively confirmed by an independent experiment of Van Attekum and Trooster.     

Electron correlation effects in the valence band photoemission spectra of cooper dichloride

He I, He II and Al Kα photoemission measurements of the valence band of CuCl₂ are reported. The presence of the 3d⁸-like satellite indicates the strong correlation effects in the final state and the breakdown of the one-particle model. It is shown that the reduction of the satellite intensity in the valence band compared with the core hole emission is caused by the delocalization of the photo-hole. The satellite intensity in resonance with the super-Coster-Kronig decay is calculated.     

Temperature independence of the angle-resolved X-ray photoemission spectra of gold and platinum valence bands

Angle-resolved valence-band X-ray photoemission spectra were taken along the [111] and [100] directions of gold single crystals and along the [100] direction of a platinum single crystal at room temperature (293 K) and on a probe cooled nearly to liquid nitrogen temperature (77 K). No change was detected on cooling the samples, in contrast to expectations based on a simple direct-transition model. A simple “matrix-element” model appears to predict spectra well even at low temperatures, perhaps because the complexity of the high-energy final-state bands permits sampling effectively throughout the zone.     

On the valence band photoemission of highT c superconductors

The valence band photoemission spectrum of highT _c -superconductors is discussed based on the half-filled single band Hubbard Hamiltonian with the strong Coulomb interaction. We discuss how to analyze these valence band and deep core level excitation spectra, concerning particularly with which orbital, Cud or Op state, a hole will occupy in the CuO₂ plane.     

Surface and bulk valence band photoemission of silicon carbide

Surface and bulk valence band photoemission spectra have been obtained for silicon carbide using Zr M-zeta (151.4eV) and Mg Kα_1,2 (1253.6eV) excitation, respectively. The data have been corrected for various broadening effects using a deconvolution procedure. Spectra for single-crystal hexagonal α-SiC and for epitaxial films of cubic β-SiC on Si (1 0 0) are compared with the results of band structure calculations. Differences in the spectra for various surface reconstructions suggest the existence of surface resonances, but no surface states are observed in the bulk optical bandgap.     

On the calculation of photoemission and related integrals

Explicit formulae are derived for the integrals which result from the application of the Gilat-Raubenheimer zonal integration method to the calculation of photoemission energy distributions. Furthermore it is shown how such formulae may be used to evaluate certain integrals required for the calculation of the imaginary part of the susceptibility of dielectric constant at zero temperature.     

Semiconductor interface studies using core and valence level photoemission

The application of core and valence level photoelectron spectroscopy to the study of semiconductor heterojunctions and metal-semiconductor interfaces (Schottky barriers) is outlined, with an emphasis on recent results and their explanation in terms of current theories. While the determination of transport barriers (valence band offsets and Schottky barriers) is stressed, the identification of chemical reactions at the interface is also discussed using several examples. Photoemission can precisely determine many important quantities in these junctions; also demonstrated, however, is the disturbing influence of the photoemission process itself through the creation of a surface photovoltage in metal-semiconductor interfaces, and its possible consequences for recent investigations of Schottky barrier heights in metal overlayers on low temperature substrates.     

Revisiting the valence-band and core-level photoemission spectra of NiO

We have reexamined the valence-band (VB) and core-level electronic structure of NiO by means of hard and soft x-ray photoemission spectroscopies. The spectral weight of the lowest energy state was found to be enhanced in the bulk sensitive Ni 2p core-level spectrum. A configuration-interaction model including a bound state screening has shown agreement with the core-level spectrum and off- and on-resonance VB spectra. These results identify the lowest energy states in the core-level and VB spectra as the Zhang-Rice (ZR) doublet bound states, consistent with the spin-fermion model and recent ab initio calculations within dynamical mean-field theory. The results indicate that the ZR character first ionization (the lowest hole-addition) states are responsible for transport properties in NiO and doped NiO.     

Theory of satellites in photoemission and inverse photoemission spectra of 4 f materials

We present calculations of the relative intensities and peak separations of the f derived spectral density for the, integer valent, light rare earths. We consider both f derived photoemission and inverse photoemission spectra. In these types of experiments, the final states has either an excess or a deficiency of charge residing on the screened by the conduction electrons. If the screening interaction is This may give rise to the appearance of satellites in both photoemission and inverse photoemission spectra. However, the calculations indicate that the relative intensity of the f derived satellite in the inverse photoemission spectrum should be extremely weak, when compared to the intensity of the satellites in the photoemission experiment.     

Giant enhancement of the valence band photoemission intensity in γ-Ce

We have observed a giant enhancement of the Ce valence band emission above the 4d absorption threshold. It is interpreted as being due to autoionization decay following 4d¹⁰4f¹ → 4d⁹4f² transitions. By taking advantage of this effect we have been able to make a determination of the location of the 4f levels in γ-Ce.     

Cooper minima in the photoemission spectra of solids

Variations of the photoionization cross section of valence states as a function of interatomic distance are studied by means of atomic and solid-state density functional approaches and compared with photoemission data. In contrast to the free atom case, a series of Cooper minima is found for 4d, 5d, and 5f states in Pd, Ag, Au, and U metals. The discovered fundamental phenomenon is of high importance for the correct interpretation of photoemission data.     

中性碳原子基态关联效应的多体理论计算

应用原子多体理论对开壳层原子中电子关联效应的有效哈密顿量及波算符的Goldston图进行了分析,在此基础上得到了计算有效哈密顿量的简单方法;以HFS模型为零级近似对中性碳原子基态的关联效应进行了计算并通过与实验结果及其他文献基于HF模型进行的计算相比较,得到了令人满意的结论。     

Effects of short-range magnetic order on photoemission and inverse photoemission spectra in iron

The dependenc of spin-resolved photoemission and inverse photoemission spectra on short-range magnetic order below and aboveT _c is investigated within a bulk interband transition model. The spectra are calculated in a 2000-atom cluster of bcc-Fe with local exchange field configurations, which are random subject to an assumed spin-correlation function. The model continuously bridges the gap between the disordered-local-moment picture (no short-range order) and a local-band picture (massive short-range order). Special emphasis is given to the analysis of factors like group velocity and the symmetry of the wave function by investigating special points in the Brillouin zone. Comparison with experimental data reveals a short-range order of at least 4 Å (corresponding to a nearest-neighbour correlation of about 0.4) nearT _c .     

Many-body calculation of dynamic quadrupole polarizability and related properties of lithium

Dynamic quadrupole polarizability of lithium atom has been calculated in its ground state using linked cluster many-body perturbation theory. Van der Waals constants have been calculated for dipole-quadrupole and quadrupole-quadrupole interactions of lithium atoms with helium and other lithium atoms. The results compare well with other available values.