4f5/2 peak

Dendrimers containing Pt " or Pt-metal nanoparticles are easily attached to Au and other surfaces by immersion in a dilute aqueous solution of the composite for 20 h, followed by careful rinsing and drying [59,129]. Therefore it is possible to use X-ray photoelectron spectroscopy (XPS) to determine the elemental composition and the oxidation states of Pt within dendrimers. For example, Pt(4f7/2) and Pt(4f5/2) peaks are present at 72.8 eV and 75.7 eV, respectively, prior to reduction, but after reduction they shift to 71.3 eV and 74.4 eV, respectively, which is consistent with the change in oxidation state from -i-2 to 0 (Fig. 13 a]. 

Fig. 17. Comparison of ringle crystal and polycrystal data of CePtj taken from Andrews et al. (1995a). Note that the 4f5/2 peak is missing in the polycrystal data even though the sample was cleaved and not scraped.

Fig. 28. Typical temperature dependence for single crystal YbAl3 between 80 K and 300 K. Spectral weight loss for the 4f,/2 peak is rarely more than 10% vs the predicted 60% in fig. 15. This is easily accounted for by Fermi function effects. There is little spectral weight loss in the 4f5/2 peak nor gain in the trivalent portion of the spectrum. Data are normalized on the Al 2p levels at -13 eV due to third-order light. (From Joyce et al. 1996.)...

The positive energy shift of the Ce 4f5/2 peak with increasing temperature was in fact first calculated by Gunnarsson and Schonhammer (1987). In that paper they also show that because of the intense and narrow iCR just above one may actually obtain an increase in measured 4f7/2 intensity at elevated temperatures despite the fact that the KR intensity is decreasing. This amplitude effect is purely a consequence of the occupation of only a small tail of a much more intense narrow feature above E. It is easy to understand this amplitude effect if the KR (or any sharp feature above f) is positioned within k T of the 300 K Fermi function (i.e., within about 20 meV of Ef) and its width is no more than about 20 meV Outside of these approximate parameters one will always get a decrease, but more importantly, in all cases there will be a shift toward the Fermi energy with the broader Fermi function. 

Fig. 43. CeBe,3(100) ARPES spectra taken at 40 eV photon energy to improve both the energy and momentum resolution. The 4f,/2 peak dispersed by about 65meV while a clear 20meV of dispersion is seen for the 4f5/2 peak, made possible by sampling a smaller portion of the Brillouin zone. The FWHM of the 4f5/2 is about 80meV, smaller than in the resonance data (from Arko et al., unpublished).

For pure WO3 the fine structure of the W(4f) peak shows considerable changes after reduction of the crystal. With the nonreduced stoichiometric crystal only two levels 4f7yj and 4f5/2 are observed, but after reduction the superposition of two doublets induces broadened features. Shifts due to the transformation of W to are revealed by a curve fitting procedure however, more drastic reduction can only be effected by hydrogen and argon ion-bombardment when W " " and W° states appear (Fig. 19). 

Similarly, peak Bi corresponds to transitions to the (4f5/2)(5d ,) configuration, while peak B2 corresponds to transitions to the (4f7/2)(5d ,) configuration. These results also indicate that the splitting between peak Bi and B2 originates from the spin-orbit splitting of Pr 4f levels. Compared with peaks A and B, the compositions of peaks C and E are complicated. Peak C corresponds to transitions to the mixed states of the (4f5/2)(5dc), (4f7/2)(5dc), (4f5/2)(5d ), and (4f7/2)(5drf) configurations which simply corresponds to the transitions from 4f states to... 

The peaks a. a2 arise from the transitions to (4f5 2)(5d ) configuration, <23 to (4f7,2)(5d ). 4 to transitions to the mixed states of (4fs 2)(5d/,) and (4f7 2)(5dj). Therefore, the difference between peaks a and a2 originates from the multiplet splitting within (4fs 2)(5dfl) configuration, i.e., the interaction between the 4fs 2 electron and 5da electron, while the difference between peaks a, a2 and peak 03 originates from the spin-orbit splitting of the Pr 4f state. Peak 04 arises from the transitions to Pr 5d/, levels. 

Figure 10. Mg -excited ESCA spectra of some lead compound mixtures, acquired in the region of the kinetic energy corresponding to the Pb 4f (4f5/2 and 4f7/2> peak-doublet transitions. The lack of collinearity among the compcsients and mixtures makes the Kalman filter separation not feasible, (a) Pb02+PbS04 (60 40) (b) Pb02+Pb(C03> (60 40) (c) Pb02+Pb(N03)2+Pb(C03) (35 35 30), (d) Pb02++Pb(C03)+Pb(S04) (20 20 60) (c) pure Pb(C03) (f) pure Pb(S04). (From Fresenius J Anal. Chem (1993) 345 490, with permissirai).

The theoretical absorption spectrum is compared with the experimental absorption spectrum (Ehrlich et al., 1979) and the experimental excitation spectrum (Reid et al., 2000) in fig. 11. The energy positions of the Ce 5d levels relative to the lowest Ce 4f5/2 level are 4.82, 5.85, 6.87, 6.97, 7.56 eV, respectively. Comparing with the experimental absorption spectrum, the relative energy positions and the relative intensity of peak B with respect to... 

Still higher resolution studies of evaporated films of y-Ce and a-Ce were carried out very recently by Patthey et al. (1985). They used the inherently sharp He resonance lines at 21.2 and 40.8 eV and a very low pass energy in their electron energy analyzer to achieve an overall resolution of 20meV. To reduce thermal broadening of the spectra of y-Ce, they cooled their samples to 150 K. (The p phase should be the stable phase at this temperature, but its spectrum is similar to that of y-Ce, based on lower energy resolution results of Wieliczka and Olson (1983).) The results of fig. 15 show that a-Ce has a structured peak at the Fermi level, while y-Ce has a peak at the Fermi level and another peak about 350 meV lower. These two were unresolved in earlier measurements and they were ascribed to spin-orbit-split 4f5 2 4f7/2 levels (see later). 

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