Fundamental Constants for Quantitative X-ray Microanalysis

2001 ◽  
Vol 7 (2) ◽  
pp. 159-167 ◽  
Author(s):  
David C. Joy
Keyword(s):  
Electron Beam ◽  
Cross Sections ◽  
Fluorescence Yield ◽  
Stopping Power ◽  
Fundamental Constants ◽  
Ionization Cross ◽  
X Ray ◽  
Electron Backscattering ◽  
Current State ◽  
Ionization Cross Sections

Abstract Quantitative X-ray microanalysis requires the use of many fundamental constants related to the interaction of the electron beam with the sample. The current state of our knowledge of such constants in the particular areas of electron stopping power, X-ray ionization cross-sections, X-ray fluorescence yield, and the electron backscattering yield, is examined. It is found that, in every case, the quality and quantity of data available is poor, and that there are major gaps remaining to be filled.

Fundamental Constants for Quantitative X-Ray Microanalysis

1999 ◽  
Vol 5 (S2) ◽  
pp. 564-565
Author(s):  
David C Joy
Keyword(s):  
Cross Sections ◽  
Stopping Power ◽  
Electron Interaction ◽  
Fundamental Constants ◽  
Absorption Coefficients ◽  
Ionization Cross ◽  
X Ray ◽  
Common Misconception ◽  
The Many ◽  
Ionization Cross Sections

The development of quantitative X-ray microanalysis in the 1950s spurred the need for knowledge of the many parameters which describe the electron interaction, such as the ionization cross-sections, fluorescent yields, the electron stopping power, mass absorption coefficients, and others. Although classical microanalysis, which proceeds by measurements of the unknown specimen against a standard, can eliminate the need to know many of these parameters accurately, much current microanalysis is done on highly inhomogeneous samples for which comparison with a standard is much less useful procedure. The increased use of low beam energies also means that data is now required for L-, and M-lines which previously have been little used. Consequently there is an enhanced need for a reliable and agreed set of data on which to base calculations.A common misconception is the belief that all of the quantities that are needed must already have been measured by somebody and so it is simply a matter of accessing this data.

MATRIX EFFECTS ON K-SHELL IONIZATION CROSS SECTIONS IN Al/Si ALLOYS

2002 ◽  
Vol 12 (01n02) ◽  
pp. 1-5
Author(s):  
M. NEKAB ◽  
Ch. HEITZ
Keyword(s):  
Cross Sections ◽  
Matrix Effects ◽  
Production Cross ◽  
Heavy Ion ◽  
Double Scattering ◽  
Scattering Mechanism ◽  
Ionization Cross ◽  
X Ray ◽  
Ionization Cross Sections ◽  
Shell Ionization

Thick targets consisting in Al/Si alloys were bombarded with 1.0 to 5.0 MeV Ar ions. The K X-ray production cross sections were deduced from the measured yields by using the Merzbacher-Lewis formula extended to heavy ion bombardment. The density dependence on the K X-ray production cross sections of Al and Si was observed. This phenomena can be interpreted within the molecular orbital double-scattering mechanism.

Ultrafast photodissociation of Br2: Laser-generated high-harmonic soft x-ray probing of the transient photoelectron spectra and ionization cross sections

2002 ◽  
Vol 117 (13) ◽  
pp. 6108-6116 ◽  
Author(s):  
Lora Nugent-Glandorf ◽  
Michael Scheer ◽  
David A. Samuels ◽  
Veronica M. Bierbaum ◽  
Stephen R. Leone
Keyword(s):  
Cross Sections ◽  
High Harmonic ◽  
Photoelectron Spectra ◽  
Ionization Cross ◽  
X Ray ◽  
Ionization Cross Sections

K-shell ionization cross sections of K and Lα X-ray production cross sections of I by 10–30 keV electron impact

2012 ◽  
Vol 90 (2) ◽  
pp. 125-130 ◽  
Author(s):  
Y. Wu ◽  
Z. An ◽  
Y.M. Duan ◽  
M.T. Liu ◽  
X.P. Ouyang
Keyword(s):  
Experimental Data ◽  
Electron Impact ◽  
Cross Sections ◽  
Production Cross ◽  
Carbon Substrate ◽  
Ionization Cross ◽  
X Ray ◽  
Pure Carbon ◽  
Ionization Cross Sections ◽  
Shell Ionization

The absolute K-shell ionization cross sections of K and Lα X-ray production cross sections of I by 10–30 keV electron impact have been measured. The target was prepared by evaporating a thin film of compound KI to a thick pure carbon substrate. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and bremsstrahlung photons produced when incident electrons impacted on the targets were corrected by using the Monte Carlo method. For K K-shell and I L-shell X-ray characteristic peaks, the spectra were fitted using the spectrum-fitting program ALLFIT to extract the Kα and Kβ peak counts more accurately for element K, and Lα peak counts for element I. The experimental results were compared with some theoretical results developed recently and available experimental data from the literature. The experimental data for I L-shell X-ray production cross sections by 10–30 keV electron impact are given here for the first time.

K-shell cross sections for analytical electron microscopy

1984 ◽  
Vol 42 ◽  
pp. 572-573
Author(s):  
Nestor J. Zaluzec
Keyword(s):  
Electron Microscopy ◽  
Cross Sections ◽  
Analytical Electron Microscopy ◽  
Relativistic Effects ◽  
Bethe Equation ◽  
Ionization Cross ◽  
X Ray ◽  
Analytical Electron ◽  
Ionization Cross Sections

There has during the last few years been a renewed interest in the calculation of ionization cross-sections for use in AEM-based x-ray analysis, due to the fact that modern AEM's can operate up to accelerating potentials of 400 kV. In this regime relativistic effects are considerable and the extrapolation of the “accepted” microprobe-based formulae to these levels is questionable and the relativistic Bethe equation is the most appropriate formulation.

Calculation and measurement of electron ionization cross sections for L and M shells

1992 ◽  
Vol 50 (2) ◽  
pp. 1642-1643
Author(s):  
Suichu Luo ◽  
David C. Joy ◽  
John R. Dunlap ◽  
Xinlei Wang
Keyword(s):  
Cross Sections ◽  
Correlation Energy ◽  
Calculation Algorithm ◽  
Ionization Cross ◽  
X Ray ◽  
Primary Mechanism ◽  
Consistent Field ◽  
Self Consistent Field ◽  
Ionization Cross Sections ◽  
Shell Ionization

The ionization of atoms by electrons is a process of great importance in physics, because it is the primary mechanism for energy loss of electron in matter and for X-ray microanalysis. Powell has critically compared various theoretical, semi- or empirical formulations with experiments and it is clear that although calculations and measurements have been carried out previously for K and to a lesser extent for L shells, very little data, both experimental and theoretical, exist for M shells.We have calculated K ,L (L1 and L23 ) and M( M1 ,M23 M45 )shell ionization cross section covering the entire periodic table and spanning the energy range from the critical ionization energy for a particular element up to 100 keV using Hartree-Slater central self- consistent field model. The calculation algorithm is essentially that described in Ref.3 but both exchange and correlation energy effects have been included in the computations to ensure that the computed cross-sections are valid at low overvoltage ratios, and relativistic corrections have also been included for accuracy at high incident energies.

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