Photoemission spectra for

The accuracy of most TB schemes is rather low, although some implementations may reach the accuracy of more advanced self-consistent LCAO methods (for examples of the latter see [18,19 and 20]). However, the advantages of TB are that it is fast, provides at least approximate electronic properties and can be used for quite large systems (e.g., thousands of atoms), unlike some of the more accurate condensed matter methods. TB results can also be used as input to detennine other properties (e.g., photoemission spectra) for which high accuracy is not essential. 

Fig. 16 K 2p core level photoemission spectra for the system Kx(Sc3N C80) as a function of increasing K intercalation level, x. The labels T and 0 refer to signals originating from K ions situated in interstitial sites of a tetrahedral or octahedral type, respectively...

Fig. 15. Photoemission spectra for solid C60 as a function of K exposure (arbitrary). The bottommost curve shows both the occupied and unoccupied density of states (from Benning et al. [38]).

Figure 2 displays photoemission spectra for the valence region of Pd/Rh(l 11) as a function of admetal coverage [32], The Pdo.9/Rh(lll) system exhibits a band structure that is very similar to that of Rh(l 11) or Pd multilayers. Difference spectra showed only minor electronic perturbations for supported palladium near the Fermi level [32],... 

Fig. 11 Valence photoemission spectra for the adsorption of CO on Ta(l 10)-supported Pd films (a) On a thick (> 3ML) Pd(l 1 l)-like film, (b) on a pseudomorphic Pd monolayer. Reprinted fi-om ref. [30].

High-resolution photoemission and first-principles DF calculations were used to study the interaction of oxygen with TiC(OOl), ZrC(OOl) and VC(OOl) surfaces [23, 24], Atomic oxygen is present on the carbide substrates after small doses of at room temperature. At 500 K, the oxidation of the surfaces is fast and clear features for TiO, ZrO or VO are seen in photoemission. Figure 6.4 shows high-resolution C Is photoemission spectra for O/ZrC(001) and OA C(OOl) surfaces. The C Is... 

Fig. 11.13. Cd 3d X-ray photoemission spectra for buik, 4.5 nn and 2.2 nm CdS nanocrystais recorded with an X-ray photon energy of 1486.6 eV (Ai-Ka). Adapted from [99].

Figure 3. The calculated photoemission spectra for the PMDA-ODA repeat unit for both Koopmans (dotted line) and ASCF (solid line) and the experimental spectrum (triangles).

These analytical considerations support the analysis and interpretation of corresponding experimental and theoretical dichroic spectra in an appreciable way. As an example of such a combined investigation, valence-band photoemission spectra for a... 

Figure 5. Photoemission spectra for U02 taken at photon excitation energies of 21.2 eV (He I), 40.8 eV (He II), and 1253.6 eV (MgKa). The uranium 5f electrons (Peak A) have a very different dependence on photon energy than the O 2p s (Peak B).

Fig. 34. Photoemission spectra for different Au coverages on GaSb (after Chye et al. [300]).

Fig. 5.7 Left spin resolved photoemission spectra for thin iron films on W(llO) taken with unpolarized light (hv = 21.22 eV). Right spin integrated spectra taken with circularly polarized radiation (hv = 21.2 eV) for emission angles between 0° < 6 < 15°. The thin lines in the MCDAD spectra mark the position of the valence band maxima in normal emission. Reprinted from [26], Copyright (1998), with permission from Elsevier...

Figure 1. X-ray photoemission spectra for 1-2-3 and 2-1-4 copper oxides. The valence bands near the Fermi level are dominated by Cu—O hybrid states. These are not affected by the substitution of rare earth ions, but new 4f related features can be identified by subtraction of the Lai gjSrg 15CUO4 baseline curve (dotted line).

Fig. 23. Measured shifts (meV) in the leading edges of the photoemission spectra for four samples, taken at cro.ssings along the Fermi surface, plotted relative to the quantity (cos, -cosA /2. Samples X III, X vn, and X III 2 exliibit strong linear correlations, consistent with an order parameter having d 2 symmetry. The extended region of zero shift in sample X V may be indicative of dirty d-wave behavior.

Fig. 14. The in-plane spin-polarized photoemission spectra for Gd(OOOl) films on W(110) at 100 K across the Gd 4f level, taken from Dongqi Li et al. (1993a). (a) the spectra of a freshly deposited film and (b) following exposure to a small amount of contamination. Spin-majority (up triangles) and spin-minority (down triangles) are indicated. The inset shows the different 4f photoemission spectra for one monolayer and ten monolayers of gadolinium (and the difference spectrum) on Cu(100) (LaGraffe et al. 1989b), illuminating the different surface...

Fig. 16. Photoemission spectra for La which have been corrected for differences in inddent photon flux for photon energies between 32 and 60 eV. The inset shows the peak height as a function of photon energy. Since there is no change in shape of the spectra, this height is proportional to the photoionization cross section. (After Wieliczka et al. 1984.)...

The discussion of section 3.2 shows that photoemission spectra for a- and y-Ce are not simple. In principle, the corresponding photoemission spectra for Ce vapor would be simpler than those of the metal because there are fewer valence electrons to respond to the photohole. Valence-electron photoemission measurements of Ce vapor have not as yet been carried out. Studies of small clusters of Ce metal have, however, been reported by Fujimori et al. (1985). 

Results for Ce clusters grown by matrix isolation in films of solid Xe were reported by Wieliczka et al. (1986). They found that small amounts of evaporated Ce exhibited only a structureless valence band EDC. The deposition of additional Ce atoms resulted in an EDC with a peak at 2 eV binding energy and a weak structure at the Fermi level. The structure at Ep grew with respect to the 2eV peak as the amount of deposited Ce increased. The many-body picture of the photoemission spectra for Ce thus requires a threshold size for Ce clusters brfore the model is applicable, but that threshold size is not yet known. 

The photoemission spectra for the Ce chalcogenides have been reported by veral authors using synchrotron radiation and resonance techniques (Gudat et al. 1981, Croft et al. 1981a,b, Weaver 1983). (See also chapter 67 of this Volume.) Those studies showed that the Ce 4f electron had an apparent binding energy in CeS of... 

Fig. 24. Photoemission spectra for the cerium pnictides taken with photon energies on resonance (122 eV, solid) and off resonance (122eV, dashed). Their difference is shown cross hatched. This technique makes it possible to highlight the 4f emission. Analogous results but with higher resolution were obtained by comparing spectra at 30 and 60 eV. As shown, the dominant feature is the one close to p for CeP but is the deeper feature for Ceffi. (After Franciosi et al. 1981.)...

Fig. 27. Photoemission spectra for CeRhj, CePdj, and Ce(Ago.3Pdo 7)3 taken on resonance (dashed) and off resonance (dotted). Their difference (solid) highlights the 4f contribution. The upper panel shows the corresponding spectra for LaPdj and demonstrates that the Pd 4d contributions have been adequately removed from the difference spectrum for the Ce compounds. (After Peterman et al. 1982.)...

Fig. 6. X-ray photoemission spectra for La and Nd thin films. Data from Baer and Busch (1973).

Fig. 5.3-2 Dots experimental normal photoemission spectra for Ag quantum wells deposited on Fe(lOO), with various thicknesses. Solid curves fits and background functions. (After [3.12])...

Fig. 78. Angular resolved photoemission spectra for (i) Pd (111), (ii) Yi5Pdg5, and (iii) Y2sPd75 films measured at room temperature and various emission angles (0—60°) and excited with He 1 resonance line (Borgschulte...

Resonant photoemission spectroscopy can give valuable information about the atomic orbital component of the state in the spectra. Figure 10 shows a plot of area intensities of the surface state induced peak for TaC(lll) as a function of the exciting photon energy. In Fig. 10, a cross section of the Ta 5d band observed in the photoemission spectra for poly-Ta (48) is also shown. The photoionization cross section for the surface state on TaC(lll) is resonantly enhanced at hv of 40 and 50 eV, as in the case for the Ta 5d band in poly-Ta. These enhancements of the cross section are well explained by the resonance process that proceeds via photon-induced excitation,... 

Figure 10 Intensities of the surface state induced peak in the normal emission spectra of TaC(lll) as a function of photon energy. Intensities of the Ta 5d band in the photoemission spectra for poly-Ta (48) are also plotted.

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