Quantitative X-Ray Emission Analysis of Magnesium Through Fluorine with X-Ray and Electron Excitation

1966 ◽  
Vol 10 ◽  
pp. 494-505 ◽  
Author(s):  
F. Bernstein ◽  
R. A. Mattson
Keyword(s):  
Matrix Effects ◽  
Electron Excitation ◽  
Emission Analysis ◽  
X Ray ◽  
Excitation Potential ◽  
Chemical Combination ◽  
Elemental Sensitivity ◽  
Powder Samples ◽  
Sensitivity Changes ◽  
Selection Of

AbstractThe analysis of dry powder samples for magnesium, sodium, and fluorine by X-ray and electron excitation has been studied. As in the case of heavier elements, the form of chemical combination influences the elemental sensitivity; sensitivity changes due to self-absorption can be adequately predicted using published absorption coefficients. Where both absorption and enhancement effects are possible, selection of X-ray target or excitation potential can. eliminate the enhancement problem. Matrix effects were found to be extremely variable and unpredictable. Finally, X-ray and electron excitation results are compared for the three elements in a series of geological samples. Efficiency of excitation was far better for electron excitation, but limits of detectability were lower for X-ray excitation due to significantly lower backgrounds.

Light Element Analysis

1969 ◽  
Vol 13 ◽  
pp. 26-48
Author(s):  
A. K. Baird
Keyword(s):  
Atomic Number ◽  
Matrix Effects ◽  
Light Element ◽  
Electron Excitation ◽  
Electron Gun ◽  
X Rays ◽  
Element Analysis ◽  
X Ray ◽  
High Emission ◽  
Quantitative Analyses

Qualitative and quantitative analyses of elements below atomic number 20, and extending to atomic number 4, have been made practical and reasonably routine only in the past five to ten years by advances in: 1) excitation sources; 2) dispersive spectrometers; 3) detection devices; and 4) reductions of optic path absorption. At present agreement is lacking on the best combination of parameters for light element analysis. The principal contrasts in opinion concern excitation.Direct electron excitation, particularly as employed in microprobe analysis (but not limited to such instruments), provides relatively high emission intensities of all soft X-rays, but also generates a high continuum, requires the sample to be at essentially electron gun vacuum, and introduces practical calibration problems (“matrix effects“). X-ray excitation of soft X-rays overcomes some of the latter three disadvantages, and has its own limitations. Sealed X-ray sources of conventional or semi-conventional design can provide useful (if not optimum) light element emission intensities down to atomic number 9, hut with serious loss of efficiency in many applications below atomic number 15 largely because of window-thinness limitations under electron bombardment.

Mineralogical Problems in X-Ray Emission Analysis of Sylvite Concentrates

1963 ◽  
Vol 7 ◽  
pp. 555-565
Author(s):  
Frank Bernstein
Keyword(s):  
Particle Size ◽  
Atomic Number ◽  
Size Effects ◽  
Quantitative Relationship ◽  
Minor Constituent ◽  
Emission Analysis ◽  
X Ray ◽  
Particle Size Effects ◽  
Chemical Combination ◽  
A Minor

AbstractMineralogical effects, which relate to the occurrence of an element in different forms of chemical combination, often are a problem to the X-ray analyst since these forms usually differ in X-ray sensitivity. An example of this is cited in connection with the analysis of sylvite concentrates for potassium. An evaluation is made of mineralogical effects and a quantitative relationship between X-ray intensity and mineral form and particle size is derived. If the particle size of a minor constituent is reduced sufficiently the mineralogical effect disappears. Target materials for X-ray sources are found to have only minor effects on relative intensities of different compounds of an element. Finally, it is concluded that the advantages of higher intensities gained through the use of target materials close in atomic number to the material being analyzed far outweigh particle size effects which are shown to be relatively small.

Measurement of “Chemical Shift” by an Automated Commercial X-ray Fluorescence Spectrometer

1976 ◽  
Vol 20 ◽  
pp. 471-479
Author(s):  
L. G. Dowell ◽  
J. M. Bennet ◽  
D. E. Passoja
Keyword(s):  
Chemical Shift ◽  
High Vacuum ◽  
Electron Excitation ◽  
Emission Lines ◽  
X Ray ◽  
The Third ◽  
Chemical Combination ◽  
Major Attention ◽  
Fluorescence Spectrometer ◽  
Sample Damage

The measurement of “chemical shift,” that is, the change in energy of an element's x-ray emission lines with the state of its chemical combination, has been carried out for some years. Of the three major aspects of the technique, two have received major attention. Nagel (1) has an excellent treatise on the interpretation of valence band x-ray spectra, while such workers as Fischer (2) and Koffman and Moll (3) have attempted to correlate the data with structure. The third area, convenient data collection, has not been so well investigated. Much, but not all, of the effort has been toward direct electron excitation with its attendant problems of sample damage due to high vacuum and electron bombardment effects.

The X-Ray Wavelength Scale in the Long-Wavelength Region

1967 ◽  
Vol 11 ◽  
pp. 241-248
Author(s):  
A. F. Burr
Keyword(s):  
Wavelength Region ◽  
Electromagnetic Spectrum ◽  
Bremsstrahlung Radiation ◽  
X Ray ◽  
Long Wavelength ◽  
Wavelength Standard ◽  
Chemical Combination ◽  
Wavelength Scale ◽  
Consistent Basis ◽  
Selection Of

AbstractRecently the X-ray wavelength scale has been put on a consistent basis by the selection of the W Kα1, line to be the wavelength standard foe the whole X-ray region of the electromagnetic spectrum. To help establish this scale, four other X-ray lines, which had been measured with a precision approaching 1 ppm, were selected as secondary standards. However, since the longest of these lines is the Cr Kα2 line at 2.293606 Å, other lines whose wavelengths are less precisely known have been used for calibration purposes. The most interesting of these is the Al Kα. line, which plays an important part in the effort to connect the X-ray wavelength scale to the basic standard of length. Two other often-used lines are the Cu La line at 13.339 Å and the O Kα line at 23.62 Å. It is, however, necessary to take several steps to trace the accepted values of these lines back to the basic X-ray wavelength standard. Furthermore, the uncertainties introduced by the effects of the chemical combination and the large natural line widths limit the precision obtainable. It has been suggested that the first resonance line of the Ne K edge in the 14-Å region would overcome both of these difficulties. It has also been suggested that the highfrequency limit of the bremsstrahlung radiation would make a particularly convenient reference mark. This method is discussed here, and it is shown that the accuracy obtainable by this method is better than that obtainable by means of some commonly used reference lines.

Problem Elements and Spectrometry Problems in X-Ray Microanalysis: the Black Holes of the Periodic Table

1998 ◽  
Vol 4 (S2) ◽  
pp. 216-217
Author(s):  
John T. Armstrong
Keyword(s):  
Black Holes ◽  
Periodic Table ◽  
Matrix Effects ◽  
Relative Concentration ◽  
Analytical Techniques ◽  
Emission Analysis ◽  
X Ray ◽  
Analysis Techniques ◽  
X Ray Absorption

Few quantitative analysis techniques attempt as large an extrapolation between the compositions of standards and samples than is attempted in electron microbeam x-ray emission analysis. In-situ x-ray microanalysis can be performed for essentially all elements in the periodic table in complex matricies that may contain, in extreme cases, thirty or more detectable elements. Analyses are attempted for the same elements, using the same standards, in various matrices whose average atomic numbers might range from 4 to 94. Unlike most analytical techniques, where suites of standards are synthesized having similar bulk compositions as the samples and bracketing the concentrations of the elements of interest, the standards employed in microbeam analysis are most commonly pure elements, simple oxides, or other binary element compounds. This is true even though matrix effects on electron retardation and scattering, x-ray absorption, and secondary x-ray fluorescence can cause major variations in the differences between relative intensity and relative concentration.

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

Influence of X-Ray Induced Fluorescence on Energy Dispersive X-Ray Analysis of Thin Foils

1977 ◽  
Vol 35 ◽  
pp. 328-329
Author(s):  
E. A. Kenik ◽  
J. Bentley
Keyword(s):  
Thin Foil ◽  
Electron Excitation ◽  
Simple Approach ◽  
Foil Thickness ◽  
X Rays ◽  
X Ray ◽  
Hole Spectrum ◽  
Illumination System ◽  
Thin Foils ◽  
Intensity Ratios

Cliff and Lorimer (1) have proposed a simple approach to thin foil x-ray analy sis based on the ratio of x-ray peak intensities. However, there are several experimental pitfalls which must be recognized in obtaining the desired x-ray intensities. Undesirable x-ray induced fluorescence of the specimen can result from various mechanisms and leads to x-ray intensities not characteristic of electron excitation and further results in incorrect intensity ratios.In measuring the x-ray intensity ratio for NiAl as a function of foil thickness, Zaluzec and Fraser (2) found the ratio was not constant for thicknesses where absorption could be neglected. They demonstrated that this effect originated from x-ray induced fluorescence by blocking the beam with lead foil. The primary x-rays arise in the illumination system and result in varying intensity ratios and a finite x-ray spectrum even when the specimen is not intercepting the electron beam, an ‘in-hole’ spectrum. We have developed a second technique for detecting x-ray induced fluorescence based on the magnitude of the ‘in-hole’ spectrum with different filament emission currents and condenser apertures.

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

X-ray microprobe for materials science

1994 ◽  
Vol 52 ◽  
pp. 56-57
Author(s):  
G.E. Ice
Keyword(s):  
Crystallographic Orientation ◽  
Local Structure ◽  
Materials Science ◽  
Chemical Information ◽  
X Ray Diffraction ◽  
Ray Optics ◽  
X Ray ◽  
Novel Materials ◽  
New Information ◽  
Elemental Sensitivity

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E≥5 keV) microprobes. With new x-ray optics these microprobes can achieve micron and submicron spatial resolutions. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature will have important applications to materials science. For example, x-ray fluorescent microanalysis of materials can reveal elemental distributions with greater sensitivity than alternative nondestructive probes. In materials, segregation and nonuniform distributions are the rule rather than the exception. Common interfaces to whichsegregation occurs are surfaces, grain and precipitate boundaries, dislocations, and surfaces formed by defects such as vacancy and interstitial configurations. In addition to chemical information, an x-ray diffraction microprobe can reveal the local structure of a material by detecting its phase, crystallographic orientation and strain.Demonstration experiments have already exploited the penetrating nature of an x-ray microprobe and its inherent elemental sensitivity to provide new information about elemental distributions in novel materials.

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