Gaussian ϕ(ρz) curves: Comparison with other models

1990 ◽  
Vol 48 (2) ◽  
pp. 192-193
Author(s):  
Alberto Riveros ◽  
Gustavo Castellano
Keyword(s):  
Good Description ◽  
Bulk Sample ◽  
Incident Electron Energy ◽  
Power Mean ◽  
General Shape ◽  
Ionization Cross ◽  
X Ray ◽  
Mass Absorption ◽  
Absorption Correction ◽  
Image Position

X ray characteristic intensity Ii , emerging from element i in a bulk sample irradiated with an electron beam may be obtained throughwhere the function ϕi(ρz) is the distribution of ionizations for element i with the mass depth ρz, ψ is the take-off angle and μi the mass absorption coefficient to the radiation of element i.A number of models has been proposed for ϕ(ρz), involving several features concerning the interaction of electrons with matter, e.g. ionization cross section, stopping power, mean ionization potential, electron backscattering, mass absorption coefficients (MAC’s). Several expressions have been developed for these parameters, on which the accuracy of the correction procedures depends.A great number of experimental data and Monte Carlo simulations show that the general shape of ϕ(ρz) curves remains substantially the same when changing the incident electron energy or the sample material. These variables appear in the parameters involved in the expressions for ϕ(ρz). A good description of this function will produce an adequate combined atomic number and absorption correction.

Use of Multiple Standards for Absorption Correction and Quantitation with Frieda

1973 ◽  
Vol 17 ◽  
pp. 269-278
Author(s):  
P. S. Ong ◽  
E. L. Cheng ◽  
G. Sroka
Keyword(s):  
Dry Mass ◽  
High Energy ◽  
Exciting Radiation ◽  
X Ray ◽  
Mass Absorption ◽  
Iron Copper ◽  
Absorption Correction ◽  
Radiation Induced ◽  
Fluorescence Radiation

AbstractThe computerized fluorescence radiation induced energy dispersive analyzer (FRIEDA) (1) described earlier uses an x-ray beam with a well defined energy for the excitation of fluorescence radiation, and an Si(Li) detector to measure the total x-ray spectra emitted. Such a system can also simultaneously provide supplemental data for the determination of the dry mass and the sample mass absorption which is necessary for accurate quantitation of the results. This instrumental capabillty has been utilized in the measurement of the trace elements iron, copper, and zinc in serum.Known amounts of two elements are thoroughly mixed with the sample. One element has a ‘high energy’ K line, the other a ‘low energy’ K line. The ratio of these intensities, in the absence of absorption, is a known constant and dependent only on the relative amounts of the respective elements, and on the energy of the exciting radiation. Whenever absorption is present, the ratio will change in a manner directly related to the mass absorption of the sample for these radiations.

scholarly journals Effect of Powder Sample Granularity on Fluorescent Intensity and on Thermal Parameters in X-Ray Diffraction Rietveld Analysis

1991 ◽  
Vol 35 (A) ◽  
pp. 57-62 ◽  
Author(s):  
C. J. Sparks ◽  
R. Kumar ◽  
E. D. Specht ◽  
P. Zschack ◽  
G. E. Ice ◽  
...  
Keyword(s):  
Rietveld Analysis ◽  
Thermal Parameters ◽  
X Ray Diffraction ◽  
General Shape ◽  
Fluorescent Intensity ◽  
X Ray ◽  
Absorption Correction ◽  
Symmetric Geometry ◽  
X Ray Absorption ◽  
Made In

AbstractThe effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu50Au44Ni6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity, A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30° 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce <5 (μm particles and high packing densities.

A Rapid Method for the Determination of Quartz in Sedimentary Rocks by X-Ray Diffraction Incorporating Mass Absorption Correction

Clay Minerals ◽  
1973 ◽  
Vol 10 (1) ◽  
pp. 51-55 ◽  
Author(s):  
M. E. Cosgrove ◽  
A. M. A. Sulaiman
Keyword(s):  
Rapid Method ◽  
Coefficient Of Variation ◽  
Sedimentary Rocks ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Rock Powder ◽  
X Ray ◽  
Mass Absorption ◽  
Absorption Correction

AbstractAn X-ray diffraction method for the estimation of quartz is described using rock powder pellets originally prepared for X-ray spectrometry, correcting the X-ray intensities for mass absorption. A coefficient of variation of 3·8% is claimed; 95% of all estimates fall within ± 5·5%.

Quantitative elemental analysis by transmission electron spectroscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 528-529
Author(s):  
David Joy ◽  
Dennis Maher ◽  
Peggy Mochel
Keyword(s):  
Cross Section ◽  
Electron Spectroscopy ◽  
Acceptance Angle ◽  
Ionization Cross ◽  
X Ray ◽  
Transmission Electron ◽  
Efficiency Factors ◽  
Image Position ◽  
Integrated Intensities ◽  
Fundamental Formula

In transmission electron spectroscopy the fundamental formula for elemental quantitation using inner-shell excitations gives the number n of atoms per cm2 contributing to the K-edge aswhere Ik and Io are the integrated intensities in the K-edge and zero-loss peak, respectively. Both of these integrals are measured for a spectrometer acceptance angle 2α and an energy interval ΔE. The parameter αk(α,ΔE) is the ionization cross-section for the same angular and energy parameters. The variation of αk with α and ΔE is a function of the generalized oscillator strength and little detailed information on this quantity is available. Therefore it is necessary to proceed empirically and the simplest assumption is thatwhere σk is a saturation (x-ray) cross-section and ηα,ηΔEcan be identified with efficiency factors.The accuracy of Equation (1) for K-edges from light elements (Li ≤ Z ≤ Al) is being tested by computer curve fitting and background stripping (see Fig. 1).

Thin film standardless analysis used in TEM asbestos EDS analysis

1988 ◽  
Vol 46 ◽  
pp. 966-967
Author(s):  
X. Li ◽  
J. Xingxing ◽  
W. Zi-qin ◽  
R. J. Lee ◽  
G. R. Dunmyre ◽  
...  
Keyword(s):  
Thin Film ◽  
Weight Percent ◽  
Atomic Weight ◽  
Fluorescence Yield ◽  
Ionization Cross ◽  
X Ray ◽  
Asbestos Fibers ◽  
Image Position ◽  
X Ray Absorption ◽  
Standardless Analysis

A thin film standardless analysis method, based on the Cliff-Loriner factor k, has been used to do quantitative x-ray analysis of asbestos fibers in the TEM. The results of the analysis of four minerals at 120 keV were close to the theoretical value. The ionization cross section Q has been revised experimentally to improve the analysis of asbestos.The Cliff-Lorimer factor has been used in TEM thin film analysis since 1975. The factor kAB is used in the following equation:CA/CB = kAB IA/IBwhere CA and CB is the weight percent of the elements A and B. The IA and IB are x-ray intensities corresponding to elements A and B. In this paper the calculated k values2 will be used for standardless quantitative analysis.In the thin film, when the effects of the backscattering electron, x-ray absorption, and secondary fluorescence are not considered, the x-ray intensity iswhere pt is the mass depth AA is the atomic weight of element A, W is the fluorescence yield, L is the ratio of the x-ray lines and T is the detector efficiency.

Quantitative X-ray microanalysis of thin specimens in the transmission electron microscope; a review

1987 ◽  
Vol 51 (359) ◽  
pp. 49-60 ◽  
Author(s):  
G. W. Lorimer
Keyword(s):  
Weight Fraction ◽  
Bulk Sample ◽  
Thin Specimen ◽  
X Ray ◽  
Qualitative And Quantitative ◽  
First Approximation ◽  
Transmission Electron ◽  
Quantitative Analyses ◽  
Image Position ◽  
X Ray Absorption

AbstractIn a thin specimen X-ray absorption and fluorescence can, to a first approximation, be ignored and the observed X-ray intensity ratios, IA/IB, can be converted into weight fraction ratios, , can be converted into weight fraction ratios, CA/CB, by multiplying by a constant , by multiplying by a constant kAB;kAB values can be calculated or determined experimentally. The major correction which may have to be made to the calculated weight fraction ratio is for X-ray absorption within the specimen. The activated volume for analysis in a thin specimen is approximately 100 000 × less than in a bulk sample. Beam spreading within the specimen can be estimated using a simple formula based on a single elastic scattering event at the centre of the specimen. Examples are given of the application of the technique to obtain both qualitative and quantitative analyses from thin mineral specimens. The minimum detectable mass and the minimum mass fraction which can be measured using the technique are estimated.

X-Ray Emission from Porous Materials : New Results

1998 ◽  
Vol 4 (S2) ◽  
pp. 206-207
Author(s):  
Raynald Gauvin
Keyword(s):  
Monte Carlo ◽  
Porous Materials ◽  
Electron Scattering ◽  
Thin Foil ◽  
X Ray ◽  
Absorption Correction ◽  
Image Position ◽  
First Time ◽  
X Ray Absorption ◽  
Electron Range

This paper present new results about x-ray emission from porous materials obtained from Monte Carlo simulations. This is an update from the results which have been presented for the first time last year. In particular, the absorption correction is now simulated in the same way as the electron scattering. In the results presented last year, x-ray absorption was calculated with the integration of the φ(ρz) curves via the usual equation :where I is the intensity emitted from the porous specimen, I0 is the intensity emitted from a thin foil with no porosity, x is the mass absorption coefficient times the cosine of the take off angle, z is the depth in the specimen and ρ is the density of the porous materials. Since the density term does not include the effect of the size of the pores, integration of this equation will give wrong results when the size of the pores are big relative to the electron range.

Quantification of Silica Uptake by Alveolar Macrophages - An Emperical Scanning Electron Microprobe Method

1982 ◽  
Vol 40 ◽  
pp. 332-333
Author(s):  
V. V. Damiano ◽  
R. P. Daniele ◽  
H. T. Tucker ◽  
J. H. Dauber
Keyword(s):  
Quantitative Analysis ◽  
Alveolar Macrophages ◽  
Bulk Sample ◽  
Silica Particles ◽  
Empirical Method ◽  
Phagocytic Cells ◽  
Calibration Standards ◽  
X Ray ◽  
Accurate Quantitative Analysis ◽  
Scanning Electron

An important example of intracellular particles is encountered in silicosis where alveolar macrophages ingest inspired silica particles. The quantitation of the silica uptake by these cells may be a potentially useful method for monitoring silica exposure. Accurate quantitative analysis of ingested silica by phagocytic cells is difficult because the particles are frequently small, irregularly shaped and cannot be visualized within the cells. Semiquantitative methods which make use of particles of known size, shape and composition as calibration standards may be the most direct and simplest approach to undertake. The present paper describes an empirical method in which glass microspheres were used as a model to show how the ratio of the silicon Kα peak X-ray intensity from the microspheres to that of a bulk sample of the same composition correlated to the mass of the microsphere contained within the cell. Irregular shaped silica particles were also analyzed and a calibration curve was generated from these data.

Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 548-549 ◽  
Author(s):  
N. J. Zaluzec
Keyword(s):  
Solid Angle ◽  
Analytical Electron Microscopy ◽  
Incident Beam ◽  
Thin Foil ◽  
Experimental Conditions ◽  
X Ray ◽  
Microchemical Analysis ◽  
Analytical Electron ◽  
Image Position ◽  
Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

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