Element Identification

REELS spectrometers are in fact Auger spectrometers, so that elemental identifications can be made easily. 

The X-ray emission process followii the excitation is the same in all three cases, as it is also for the electron-induced X-ray emission methods (EDS and EMPA) described in Chapter 3. The electron core hole produced by the excitation is filled by an electron falling from a shallower level, the excess energy produced being released as an emitted X ray with a wavelength characteristic of the atomic energy levels involved. Thus elemental identification is provided and quantification can be obtained from intensities. The practical differences between the techniques come from the consequences of using the different excitation sources. 

Static SIMS entails the bombardment of a sample surface with an energetic beam of particles, resulting in the emission of surface atoms and clusters. These ejected species subsequendy become either positively or negatively charged and are referred to as secondary ions. The secondary ions are the actual analytical signal in SIMS. A mass spectrometer is used to separate the secondary ions with respect to their charge-to-mass ratios. The atomic ions give an elemental identification (see... 

The interpretation phase consists of three elements identification of significant issues, evaluation by various checks and conclusions, and giving recommendations and reporting (Fig. 15.5). 

This Study has shown that reasonably uniform platinum crystallites can be made on y-alumlna, and that platinum and palladium can be segregated and maintained In that form for the most part even after exposure to high temperature oxidation-reduction conditions. Highly dispersed clusters of palladium, nickel, cobalt, and Iron can be observed. Cluster size determination could not be accurately made because of the lack of contrast between the cluster and the support. The marginal detectability by EDS for these clusters enabled elemental Identification to be made, however, mass uniformity determinations could not be made. 

Auger atlases can be used in applied AES for rapid preliminary elemental identification, although comparison of the spectra from any two adjacent elements in such atlases reveals that the relative intensities of different Auger transitions within... 

Element Identification Year of Issue Chemical form... 

XRF offers a unique approach for rapid, non-destructive elemental analysis of liquids, powders, and solids. Although the first row transition elements are the most sensitive, elements from atomic number 12 (magnesium) and greater can be measured over a dynamic range from trace (ppm) to major (percent) element concentrations. EDXRF is well suited for qualitative elemental identification of unique samples, while WDXRF excels at high precision quantitative analysis. 

Elemental Identification Excellent Excellent Good Good... 

Co mposition/pur ity elemental identification AES, XPS, SIMS, ISS, RBS, EELS (Core level), APFIM, NRA, PIXE, GDMS, GDOS, SCANHR, EDX, laser microprobe, and electron microprobe... 

While XPES has been applied extensively for the examination of changes in chemical environment, uses of AES have been concentrated on elemental identification and quantification, particularly in the case of... 

X-ray sources X-ray fluorescence analysis is a technique for elemental identification and quantification. X-ray fluorescence sources provide stable outputs for energy, direction and intensity. Unlike competing technologies, radioisotope sources do not require external power supplied. 

Favreau LV, Pickett CB. 1995. The rat quinone reductase antioxidant response element. Identification of the nucleotide sequence required for basal and inducible activity and detection of antioxidant response element-binding proteins in hepatoma and non-hepatoma cell lines. J. Biol. Chem. 270 24468-74... 

Spent catalysts were also investigated with a Philips EM 30-ST HREM equipped with EDX for element identification. 

Modern X-ray spectrometers are equipped with computer software that is fully capable of identifying the possible elements from a spectrum. We can input the elements that possibly exist in the specimen into the software for qualitative analysis. The computer software will mark peak positions of the input elements in the spectrum. Also, the software will generate such peak lines with correct relative intensities in a spectrum, for example, a correct intensity ratio of Ka to Kfi. With computer assistance, the errors in element identification can be reduced to minimum. 

Peak positions in an XPS spectrum are likely to be affected by spectrometer conditions and the sample surface. Before XPS peak identification, we often need to calibrate the binding energy. Calibration is particularly important for samples with poor electrical conductivity. Calibration can be done with an internal standard that has a peak that shows little or no chemical shift, for example, elemental Si. The most common method is use of the C Is peak at 285 eV from carbon adsorbed on the sample surface. The carbon from organic debris (as C—H or C-C) in air is found on all samples exposed to the environment. The peaks of core level binding energies as listed in Table 7.1 are sufficiently unique for element identification. 

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