Satellite structures

Special attention was paid to the detection of residual Cu-fl quantities accompanying the metallic Cu. The relative amounts of Cu+1 and Cu were determined by curve-fitting the Cu (LMM) spectra using the Physical Electronics Version 6 curve-fitting program. The catalyst showed reduction of Cu+2 Into a mixture of Cu+1 and Cu after reduction In H2 at 250 C for one hour (Figure 6) as evidenced by the two resolved peaks In the Cu (LMM) spectrum at 568.0 and 570.3 eV which are characteristic of Cu and Cu+1, respectively, and by the disappearance of the Cu+2 2p satellite structure. It could be shown that less than 2%, If any, of the total Cu could be present In the +1 oxidation state during methanol formation. However, when the catalyst was briefly exposed to air (1 minute), a few percent of Cu+1 readily formed (7). Thus, any kind of oxidation environment has to be avoided between methanol synthesis and catalyst analysis. Otherwise, appreciable amounts of Cu+1 will be detected. 

Another consideration is the natural line width and satellite structure of the x-ray line used. Titanium (TiKa=4510.9 eV) has seen limited use (12) for non-destructive depth profiling, but the observed spectra are complicated by the TiKa satellite structure and the large natural line width of 2.0 eV (13). 

Fig. 56. TEM images of DNA-linked gold network (a) an assembly of 8 and 30 nm gold particles (b) higher resolution image of (a) (c) control experiment without DNA (d) HR-TEM image of a portion of a hybrid Au/quantum dot (QD) assembly. The lattice fringes of the QDs, which resemble fingerprints, appear near each Au nanoparticle, (e) A satellite structure formed using a 60-fold excess of the 8 nm particles. Reproduced with permission from Ref. (185). Copyright 2000, American Chemical Society.

For an approximate determination of the sample composition it is often sufficient to measure the peak height of the core level. In general, however, core level structures are asymmetric peaks above a finite background and sometimes accompanied by satellite structures. These structures originate from the many-body character of the emission process. Therefore a peak integration including satellites and asymmetric tails is much more reliable. Due to the above difficulties quantitative analysis of XPS data should be taken as accurate to only within about 5-10%. 

Fig. 14 Co 2p3 j2 spectra for a CoP and b Co metal. The inset in a shows the low-intensity satellite structure. Reprinted with permission from [58], Copyright the American Chemical Society...

How then, can one recover some quantity that scales with the local charge on the metal atoms if their valence electrons are inherently delocalized Beyond the asymmetric lineshape of the metal 2p3/2 peak, there is also a distinct satellite structure seen in the spectra for CoP and elemental Co. From reflection electron energy loss spectroscopy (REELS), we have determined that this satellite structure originates from plasmon loss events (instead of a two-core-hole final state effect as previously thought [67,68]) in which exiting photoelectrons lose some of their energy to valence electrons of atoms near the surface of the solid [58]. The intensity of these satellite peaks (relative to the main peak) is weaker in CoP than in elemental Co. This implies that the Co atoms have fewer valence electrons in CoP than in elemental Co, that is, they are definitely cationic, notwithstanding the lack of a BE shift. For the other compounds in the MP (M = Cr, Mn, Fe) series, the satellite structure is probably too weak to be observed, but solid solutions Coi -xMxl> and CoAs i yPv do show this feature (vide infra) [60,61]. 

Figure 4 is a good example of satellite structure associated with a surface species. The chromium 2p /2,l/2 spectrum results from the reaction of the dichromate ion,, with galena to yield both... 

The XPS results for cobalt at pH 4, particularly the Co 2p splitting (15 eV) and the absence of shake-up satellite structure, are indicative of cobalt(III). However, the N(amine)/Co atomic ratio of 2.7 indicates that some ammonia ligands have been displaced. Since it is known (22) that hydrolysis rates for cobalt(III) complexes are very slow, the presence of cobalt with a low number of coordinated amines, suggests that hydrolysis is induced via an interaction with the birnessite surface. The cobalt to manganese ratios for bulk and surface measurements are equivalent within experimental error, a result which is consistent with a reaction process occurring primarily at the surface. It is... 

XPS studies have been made on a number of compositions of these transition-metal oxides, and all indicate predominantly divalent nickel. Thus, for the 442 compound the Co spectrum is clearly Co +, and the Mn spectrum can be assigned to 80% Mn" + with 20% Mn +. The Ni spectrum is characterized by an intense and complicated satellite structure and consistent with 80% NP+ and 20 NP+. Studies on LiNio.33Mno.33Coo.3302, LiNio.5Mno.502, and... 

Partial localization of the 5 f states in the light actinides (line III of subsection b) might cause the appearance of satellite structures at energies not very far from Ep in their valence band photoemission spectra. If such structures could be convincingly demonstrated, important information would be added to the theoretical analysis of the locahza-tion vs. itineracy problem of the actinide metal series. 

The crucial experiment to identify whether this satellite structure is due to a localized 5 f hole, is claimed to be photoemission spectroscopy, in which the excitation (provided by synchrotron radiation) is tuned through the 5d-5f threshold energy . At the threshold energy an empty 5 f state just beyond Ep becomes occupied... 

Fig. 15. Angle-integrated photoelectron energy distribution curves of uranium in the region of the giant 5 d -> 5 f resonance (90 eV < hv < 108 eV). The 5 f intensity at Ep is suppressed by more than a factor of 30 at the 5 ds/2 threshold (see the spectra for hv = 92 and 94 eV) and resonantly enhanced above threshold (see, e.g., the spectrum for hv = 99 e V). At an initial energy 2.3eV below Ep a new satellite structure is observed which is resonantly enhanced at the 5 d5/2 and 5 ds onsets. At threshold the satellite coincides with the Auger electron spectrum, which moves to apparently larger initial energies with increasing photon energy (from Ref. 67)...

Because of the much reduced itinerant 5 f character of Pu one would expect a similar, but even more pronounced multielectron satellite structure as observed at 2.3 eV in U. In contrast to U, this satellite due to a localized 5f hole state screened by (6d7s) conduction electrons should not be a single line but show three or even four separate components as calculated for the 5 f 5 f final state multiplet . The fact that such a multiplet satellite is not observed in the XPS valence band spectrum is confusing. It could... 

Schneider and Laubschat attribute to a two-hole satellite the 10 eV structure which has been observed (see Table 3) by some authors. This structure is at 7 eV higher binding energy than the main 5 f peak, in the spectrum of UO2. It disappears, however, for in situ scraped single crystals. A similar satellite structure appears in PUO2 at 9... 

It is gratifying to note that the theoretical calculations on model systems reproduce the trends shown in Fig. 46 providing strong confirmation for the overall validity of the interpretations32 36. Low energy shake up satellite structures are often highly characteristic of the n electronic structure of the pendant group as is clear from a comparison of Fig. 43 and Fig. 47. In each case theoretical analysis indicates... 

Having identified and qualitatively understood the main features of the low energy satellite structures arising predominantly from shake up processes0, we may... 

The Cr 2p3a binding energies (XPES) increase from Cr(CNPh)6 to [Cr(CNPh)6]+ to [Cr(CNR)6]2+, the values being 574.5, 575.3 and 576.7 eV respectively.22 29 The shake-up satellite structure associated with the N Is and C Is binding energies in these spectra most probably arises from M (d)- it (CNAr(R) excitations accompanying the primary photoemission. 

Beryllium is used in satellite structures in the form of both sheet and extruded tubing and is a very important material for all types of space optics. Beryllium oxide ceramic applications take advantage of high room temperature thermal conductivity, very low electrical conductivity, and high transparency to microwaves in microelectronic substrate applications. 

If we examine Eq. (21.14) and Fig. 21.5 it is apparent that apart from v2 = vb, the cross section has zeroes when v2 = vb(mod 1). Furthermore, the combination of these zeroes and the periodic variations in A lead to satellite structure which is... 

Shake-up satellite structure in the X-ray photoelectron spectra of [Mo(CNR)7](PF6) (R = Me, Bu, C6H,) has been observed. The similarity of the nitrogen band carbon s Is/lp ratios to those of Mo(CO)6 oxygen b and carbon b Is/lp ratios argues for a similarity in bonding, as a decrease in the metal-carbon bond length (i.e., stronger M-C bonding) will influence both the satellite position relative to the primary peak and the Is/lp intensity ratio (266). 

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