X-ray Spectroscopy for Elemental Analysis

Spectroscopic characterization is also important in the study of oxide minerals. Among the many methods (Sections 7.3 through 7.7), it is important to mention X-ray fluorescence (XRF, Section 7.3.3), which allows a rapid elemental analysis of mineral samples. Electron microscopy allows observation of clay fraction particles shape and, coupled to X-ray spectroscopy, also elemental analysis (Section 7.5). Infrared spectroscopy (Section 7.4.3) is also frequently employed here, difference spectra combined with selective extraction procedures (Hass and Fine 2010) can be used to identify and study minor components (Golden, Dixon, and Kanehiro 1993). Nuclear magnetic resonance (NMR, Section 7.4.4) is in some cases useful (with uneven spin nuclei), for example, to distinguish octahedral and tetrahedral A1 centers (Bertsch and Parker 1996). 

Surface analysis (AES/XPS) Electron spectroscopy for elemental analysis of surfaces, sensitive to as low as two atomic layers. Physical electronics model PHI-570 Auger Electron Spectroscopy/X-ray Photoelectron Spectroscopy System is a double pass cylindrical mirror energy analyzer with dual anode (Mg/Al) X-ray source and has a rapid sample introduction probe. It can detect elements at the first five to ten atomic layers of sample and detect all elements except H and He. 

Direct methods of analysis such as ultraviolet (UV) absorption, infrared spectroscopy (IR), fluorescence, phosphorescence [13], X-ray fluorescence [14-16] and thermal analysis [17] have been reported. However, these methods generally lack specificity [18]. In Fourier transform IR (FTIR), overlapping bands of other species may interfere with the absorbance bands of the analyte, and in UV analysis the absorbance bands of different antioxidants can be very similar. UV and FTIR analysis are especially useful techniques when an antioxidant system is already known. X-ray fluorescence and elemental analysis are fast and useful techniques for the determination of antioxidants containing phosphorus or sulfur. The measurement of oxygen consumption... 

All M2-naph were characterized by and NMR spectroscopy, X-ray crystallography, and elemental analysis. While the proton chemical shifts of the scandium, yttrium, and lutetium naphthalene complexes were close to each other, the proton chemical shifts of the naphthalene fragment in La2-naph were shifted significantly upfield compared with the other three complexes (Table 2). However, it was found that the chemical shifts for La2-naph were similar to those of other rare earth naphthalene complexes (Huang and Diaconescu, 2013). 

X-ray photoelectron spectroscopy (XPS), also called electron spectroscopy for chemical analysis (ESCA), is described in section Bl.25,2.1. The most connnonly employed x-rays are the Mg Ka (1253.6 eV) and the A1 Ka (1486.6 eV) lines, which are produced from a standard x-ray tube. Peaks are seen in XPS spectra that correspond to the bound core-level electrons in the material. The intensity of each peak is proportional to the abundance of the emitting atoms in the near-surface region, while the precise binding energy of each peak depends on the chemical oxidation state and local enviromnent of the emitting atoms. The Perkin-Elmer XPS handbook contains sample spectra of each element and bindmg energies for certain compounds [58]. 

Other techniques in which incident photons excite the surface to produce detected electrons are also Hsted in Table 1. X-ray photoelectron Spectroscopy (xps), which is also known as electron spectroscopy for chemical analysis (esca), is based on the use of x-rays which stimulate atomic core level electron ejection for elemental composition information. Ultraviolet photoelectron spectroscopy (ups) is similar but uses ultraviolet photons instead of x-rays to probe atomic valence level electrons. Photons are used to stimulate desorption of ions in photon stimulated ion angular distribution (psd). Inverse photoemission (ip) occurs when electrons incident on a surface result in photon emission which is then detected. 

X-rays provide an important suite of methods for nondestmctive quantitative spectrochemical analysis for elements of atomic number Z > 12. Spectroscopy iavolving x-ray absorption and emission (269—273) is discussed hereia. X-ray diffraction and electron spectroscopies such as Auger and electron spectroscopy for chemical analysis (esca) or x-ray photoelectron spectroscopy are discussed elsewhere (see X-raytechnology). 

Si(Li) spectroscopy, with the capability of simultaneous quantitative analysis of 72 elements ranging from sodium through to uranium in solid, liquid, thin film and aerosol filter samples. The penetrating power of protons allows sampling of depths of several tens of microns, and the beam itself may be focussed, rastered or varied in energy. The use of a proton beam as an excitation source offers several advantages over other X-ray techniques, for example there is a higher rate of data accumulation across the entire spectrum which allows for faster analysis. 

Direct measurement of the absolute binding energy and widths of core (X-ray) and valence (UV) bands. The core levels do not participate in bonding, hence each element gives a characteristic XPS spectrum electron spectroscopy for chemical analysis (ESCA). ESCA gives the elemental composition of the surface of a solid sample (except H), the relative amounts of each element present, its oxidation state and some information on the chemical environment around each element. In addition, it is capable of providing an estimate of the depth of a deposited overlaycr... 

X-ray photoelectron spectroscopy (also called electron spectroscopy for chemical analysis, or ESCA) is a surface technique that can be used to detect elements qualitatively (and quantitatively, in some cases) in the surface layers of solids, as well as the chemical states (species) of the elements. The basic experimental apparatus for performing XPS studies includes an x-ray source (most commonly,... 

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