Origin of X-Ray Spectra

X-Rays. If an x-ray is emitted, it has an energy, AE, equal to the difference in the binding energies of the two atomic shells, E — Ej. If the original hole is in the K shell, the x-ray is called a K x-ray if the hole is in the L shell it is an L x-ray. Because the hole can be filled by an electron from any of the several outer shells, x-ray spectra contain a large number of discrete lines. 

The production of characteristic X rays is determined by the cross sections discussed above, but the observed X-ray spectra include both these characteristic peaks and a continuous background radiation. A detailed investigation of the origin of... 

The very close similarity between the x-ray spectra of the different elements shows that these radiations originate... 

The origins of analytical electron microscopy go back only about 15 years when the first x-ray spectra were obtained from submicron diameter areas of thin specimens in an electron microscope [1]. Characterization of catalyst materials using AEM is even more recent[2,3] but is currently a very active research area in several industrial and academic laboratories. The primary advantage of this technique for catalyst research is that it is the only technique that can yield chemical and structural information from individual submicron catalyst particles. 

The basis for the claim of discovery of an element has varied over the centuries. The method of discovery of the chemical elements in the late eightenth and the early nineteenth centuries used the properties of the new sustances, their separability, the colors of their compounds, the shapes of their crystals and their reactivity to determine the existence of new elements. In those early days, atomic weight values were not available, and there was no spectral analysis that would later be supplied by arc, spark, absorption, phosphorescent or x-ray spectra. Also in those days, there were many claims, e.g., the discovery of certain rare earth elements of the lanthanide series, which involved the discovery of a mineral ore, from which an element was later extracted. The honor of discovery has often been accorded not to the person who first isolated the element but to the person who discovered the original mineral itself, even when the ore was impure and that ore actually contained many elements. The reason for this is that in the case of these rare earth elements, the earth now refers to oxides of a metal not to the metal itself This fact was not realized at the time of their discovery, until the English chemist Humphry Davy showed that earths were compounds of oxygen and metals in 1808. 

The calculation of x-ray emission spectra of molecules or solids are one of the most successful applications of the discrete variational (DV) Hartree-Fock-Slater (Xa) MO method using cluster approximation [8-10], which was originally coded by Ellis and his CO workers [11-14] based on Slater s Xa exchange potential [15]. The DV-Xa method has several advantages for the calculation of x-ray transition process as follows. 

The peaks A and B in both spectra clearly originate from the noncrystalline domain in the samples, indicating that the noncrystalline domain reported from X-ray diffraction has a relatively ordered structure rather than a randomly distributed one. This conclusion derived from NMR is also supported by the conclusion that the noncrystalline domain is highly oriented in aromatic polyamides on the basis of X-ray diffraction studies [30, 32], The relatively broad peaks show a wider distribution for each 0nh value compared with peak C, which is also reasonable. The chemical shieldings of the peaks A and B are almost the same between PMIA and P4M-MPTA. This indicates that the local structure in the noncrystalline domain is similar for these polyamide fibers. It has been reported that the fraction of noncrystalline domain in the P4M-MPTA sample is higher than in the PMIA sample. The increase in the fraction of the noncrystalline domain comes predominantly from the contribution of peak A, i.e., the structure with 0nh = 31-42°, which is derived from the solid-state NMR experiment. 

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. 

We ran a number of experiments with Ge deposited on Si(OOl) wafers and studied the morphology with inelastic peak shape analysis of X-ray excited electron spectra. Additional measurements by Rutherford backscattering (RBS) and atomic force microscopy (AFM, see Part IV) were performed to give complementary information on the nanostructure of this system. For details of the experiment and the data analysis the reader is referred to the original publications [ 127,128]. 

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