Shake-up peaks

The selection rules appropriate for a shake-up transition are of the monopole type2, 76. The intensity of a shake-up peak depends on the overlap integral between the lower state molecular orbital from which the electron is excited (in the neutral molecule) and the upper state molecular orbital to which the electron is excited (in the core-ionized molecule). Consequently one expects transitions of the type au au, ag " ag> 7T nu, and irg - ng with g u and u - g transitions forbidden. 

As a first, trivial, example of the application of the overlap criterion, let us consider the possibility of a shake-up peak associated with the C Is ionization of the terminal carbon atom in nitroethane and the v - v transition of the nitro group in that molecule. In this case the core ionization occurs in a region of the... 

The core ionization of an atom stabilizes all the valence electrons in the atom. Depending on whether the electronic transition shifts electron density to or from an atom, the energy separation for a shake-up peak of that atom will be less than or greater than the energy of the neutral molecule ionization81. As an illustration of these effects, let us consider the shake-up spectra of formamide, H2NCH082. The principal transitions involved are the vl - n3 and 7r2 - 7r3 transitions. The tTj... 

As one goes to metals of higher Z, the intensities of the shake-up peaks increase. 

Although shake-up peaks are present in the case of metal ions with vacant or partially filled 3d shells, they are absent in the case of ions with completely filled 3d shells. 

Relative to at 285.0 eV, A given with respect to centroid of asymmetric shake-up peak. 

Similar effects have also been observed for solids and seem to become a very important source of information, because for a given ion the satellites are found to depend in intensity, position and shape on the type of ligand in transition metal complexes 24,13s,im, 174,175) Thus in many cases the study of shake-up peaks has provided additional evidence for a specific oxydation state 17> and will certainly increase our understanding of crystal and ligand field effects. 

The chemical shift of "x- 1.5 eV for the core level peak in PEO, relative to PS, can be attributed to each carbon being attached to an oxygen atom and is consistent with theoretical predictions and experimental results on related low-molecular-weight model compounds. (4, 16) As expected, there is no shake-up peak in The core level spectrum for PEO since the poljroer is fully saturated. (17) These significant differences in XPS spectra of PS and PEO, i.e., the 1.5 eV chemical shift in the core levels, the uniqueness of the ir -it shake-up peak... 

XANES is one of powerful tools for the study of chemical states of lanthanoid compounds. Most of the conclusions drawn from the XANES for the lanthanoid compounds have been concerned with the chemical states or characteristics of the electronic structures. In particular, valences of lanthanoids have been studied using such spectra (2). They were obtained by assigning some of the peaks in the spectra to different valences. By using the Anderson impurity model, the valences were derived from intensities of shake-up peaks (3). 

Figure 7.10 Examples of several types of satellite peaks in XPS spectra (a) shake-up peaks in a CuO spectrum (b) shake-up peaks and multiplet splitting in a NiO spectrum and (c) plasmon loss peak in a clean A1 spectrum. (Reproduced with permission from J.F. Watts, An Introduction to Surface Analysis by Electron Spectroscopy, Oxford University Press, Oxford. 1990 Royal Microscopy Society.)...

Fig. 5.14 Evolution ofXPS C Is spectra of F8BT with increasing Cs coverage. The two shake-up peaks (peak jt (l) and peak Jt (2)) and an extra peak that may be related to...

From the inset of Fig. 5.20(c), we observe clearly the alternation of the shake-up features of the C Is core level upon CsF and Yb deposition. The CsF deposition does not affect the shake-up peaks, but 3 A of Yb immediately destroys one of them at a lower binding energy. This result is analogous to that obtained at the Cs/PFO and Cs/F8BT interfaces, indicating that the LUMO is broadened by the metal deposition by a charge-transfer process. Therefore, unlike the case of Yb/CsF/Au, the liberated Cs is not in the metallic state and instead it immediately... 

Section lll.C describes how the inclusion of some of the basis operators from the 3-block in the EOM P-space is important for the calculation of the main peaks in the N2 spectrum. Once this is done, the increased dimensionality of the partitioned EOM matrix leads to the appearance of additional roots of the EOM pseudoeigenvalue problem. If the 3-block basis operators, which are moved to the P-space, correspond to the major components of the ionization operators for the shake-up lines, the new roots of the EOM matrix give the positions of these shake-up peaks. Thus the shake-up energies are naturally produced by the EOM method given our generalized definition of the EOM P space... 

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