Soft x-ray spectra

Soft X rays (wavelength 5-500 A) are probably the most generally applicable of all spectroscopic tools, yet they have not been widely used for the characterization of solids. These methods are likely, however, to 

An important advantage of the soft X-ray method is that spectra appear unaffected by the degree of long-range order thus, the technique can be applied to the study of crystalline and amorphous materials with equal facility. 

X-ray absorption methods are sometimes used for routine chemical analyses, although in most cases. X-ray fluorescence is 

Absorption-edge methods also provide information about the bond type, as judged from spectral profiles for covalent, metallic, and ionic compounds. It is too early to predict accurately the extent to which the technique can be adopted for routine characterization of the crystal chemistry of materials. 

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Fig. 5.32. X-ray photoelectron and x-ray emission spectra for BjO,. The O 2s and valence-band x-ray photoelectron (ESCA) spectra (obtained using A1 Ka radiation) are shown aligned with the oxygen K and boron K x-ray emission spectra ( soft x-ray spectra, SXS). Peak 1 in the ESCA spectrum is B Is peak II is O 2p. Spectra were aligned using li core-level binding energies (after Joyner and Hercules, 1980 reproduced with the publisher s permission).

Figure 37. Soft X-ray spectra of (a) Cd and (b) In AC,5 edges compared to (c) In 3d XPS spectra. Strong effects of particle size are seen in the soft X-ray edge stmcture. After Hamad et al. (1999).

These elements possess well-developed multiplet structure in the soft X-ray spectra of the condensed phase, which can be compared with the spectrum of the free atom by performing ah initio Dirac-Fock calculations, the actual 4/ occupancy in the solid can be deduced. An example is shown in fig. 11.4 The first point to note is that the multiplet structure of the atom survives in the solid, because of the strong localisation of the 4/ electrons (see section 5.6), so that soft X-ray spectroscopy provides a... 

Finally, a subject of fundamental importance in atomic physics is the study of how electronic properties are modified by the atomic environment, as in molecules or in the solid state. New situations have been found at the frontier between atomic physics, molecular physics and the physics of condensed matter. This area has grown considerably with the discovery of giant resonances which, though atomic in origin, were first observed in the soft X-ray spectra of solids. Since then, resonant photoemission has become a well-established experimental technique in solid state physics, and valence fluctuations and intermediate valence effects in solids have been shown to involve localised orbitals which are partly atomic in character. 

Band width (fiom soft X-ray spectra) Electronic specific heat... 

D.J. Fabian, Soft X-Ray Band Spectra, Academic Press, London, 1968. 

With the semiconducting oxides, we expect anionic chemisorption to occur over the lattice cations, and our simple molecular orbital theory will be adequate if the conduction band is associated mainly with the cation lattice. This is certainly the case with AI2O3, where there is direct evidence in the soft X-ray emission spectra that the highest filled band is the oxygen 2p band 16). 

Munakata, N. Hieda, K. Usami, N. Yokoya, A. Kobayashi, K. Inactivation action spectra of Bacillus subtilis spores with monochromatic soft X rays (0.1-0.6 nm) of synchrotron radiation. Radiat. Res. 1992, 131 (1), 72-80. 

We conclude that future satellite observations of SN 1987A with high sensitivity soft X-ray detectors should be critical in order to test the evolution theories of young neutron stars. This goal may very well be realized within the next 10 years, by the programs such as ROSAT, SXO, GRANAT, SPECTRA, and AXAF. 

Soft X-ray spectroscopy has been used to investigate the 3d electron distribution in small Ni particles.179 180 In addition to showing modified absorption and emission spectra, the small Ni particles (< 2 nm) have two satellite peaks in the absorption spectrum missing. This is attributed to a loss of long range order due to small particle size. 

The first experimental observations of the absence of core levels seem to have been made by Lukirskii et al.1 and Codling and Madden2 in soft X-ray absorption spectra for Xe. They found lines converging to what seemed to be the 4 3/2 threshold but no lines were found that could be associated with the 4p1/2 threshold. Later photoabsorption experiments on Te3), Xe4 and Cs5 confirmed these results for Xe and Cs and showed that in Te both 4p-thresholds were absent (see also Sect. 9). 

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