Elemental specification

AES Auger electron spectroscopy After the ejection of an electron by absorption of a photon, an atom stays behind as an unstable Ion, which relaxes by filling the hole with an electron from a higher shell. The energy released by this transition Is taken up by another electron, the Auger electron, which leaves the sample with an element-specific kinetic energy. Surface composition, depth profiles... 

Figure Bl.25.6. Energy spectrum of electrons coming off a surface irradiated with a primary electron beam. Electrons have lost energy to vibrations and electronic transitions (loss electrons), to collective excitations of the electron sea (plasmons) and to all kinds of inelastic process (secondary electrons). The element-specific Auger electrons appear as small peaks on an intense background and are more visible in a derivative spectrum.

The Extended Iliickel method also allows the inclusion ofd orbitals for third row elements (specifically, Si. P, Sand CD in the basis set. Since there arc more atomic orbitals, choosing this option resn Its in a Ion ger calc ii 1 at ion. Th e m ajor reason to in cin de d orbitals is to improve the description of the molecular system. 

In a closed-shell system, P = P) = P and the Fock matrix elements can be obtained by making this substitution. If a basis set containing s, p orbitals is used, then many of the one-centre integrals nominally included in INDO are equal to zero, as are the core elements Specifically, only the following one-centre, two-electron integrals are non-zero (/x/x /x/x), (pit w) and (fti/lfM/). The elements of the Fock matrix that are affected can then be written a." Uxllow s ... 

Gives complexes of constrating colors with AI,Zn, Th. Zr, and Ga and is useful in tlie photometric analysis of these elements specific reagent of Pa(H) spectrophotometric determination of Cu(U)... 

Applications Linked to Physical Properties. Apphcations involving physical properties use high purity (>99.99%) lanthanides and exploit the elements specific electronic configuration. 

All elements, but not element specific No, except in special cases of electron-beam damage 4-20 A... 

Range of elements Magnetic materials only not element specific No... 

Cathodoluminescence, CL, involves emission in the UV and visible region and as such is not element specific, since the valence/conduction band electrons are involved in the process. It is therefore sensitive to electronic structure effects and is sensitive to defects, dopants, etc., in electronic materials. Its major use is to map out such regions spatially, using a photomultiplier to detect all emitted light without... 

EXAFS is a nondestructive, element-specific spectroscopic technique with application to all elements from lithium to uranium. It is employed as a direct probe of the atomic environment of an X-ray absorbing element and provides chemical bonding information. Although EXAFS is primarily used to determine the local structure of bulk solids (e.g., crystalline and amorphous materials), solid surfaces, and interfaces, its use is not limited to the solid state. As a structural tool, EXAFS complements the familiar X-ray diffraction technique, which is applicable only to crystalline solids. EXAFS provides an atomic-scale perspective about the X-ray absorbing element in terms of the numbers, types, and interatomic distances of neighboring atoms. 

Future trends will include studies of grain-dependent surface adsorption phenomena, such as gas-solid reactions and surface segregation. More frequent use of the element-specific CEELS version of REELM to complement SAM in probing the conduction-band density of states should occur. As commercially available SAM instruments improve their spot sizes, especially at low Eq with field emission sources, REELM will be possible at lateral resolutions approaching 10 nm without back scattered electron problems. 

Most electron probes have more elemental specificity. 

The element specificity of atomic absorption spectrometry has also been used in conjunction with gas chromatography to separate and determine organo-metallic compounds of similar chemical composition, e.g. alkyl leads in petroleum here lead is determined by AAS for each compound as it passes from the gas chromatograph.75... 

TROUT ETAL. Element-Specific Epifluonscoux Micmscopy... 

Destructive techniques have been widely applied to determine the concentration of key elements In cells and other biota, but beside being Incapable of use in vivo, they offer no Information on the chemical nature of the element In question. For example, acid digestion of cells which have accumulated various organotln species, and subsequent traditional analysis by atomic absorption (AA) spectroscopy or element-specific spectrofluorlmetry, will produce quantitative data on the amount of tin present, but will reveal nothing about the coordination environment of the metal on the cell surface prior to destruction. 

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