Measurements of absolute cross sections for K-shell ionization of Fe and Mn by electron impact

Llovet, Xavier; Merlet, Claude; Salvat, F.

doi:10.1088/0953-4075/35/4/320

Cited by 25 publications

(24 citation statements)

References 16 publications

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“…The estimated error reported for the experimental cross sections was ϳ10-11%. The differences between our calculations and the experimental data of Llovet et al ͓15,35͔ are, in general, less than this error estimate, except for copper where the average difference was ϳ15%. In all cases, however, the shape of the calculated cross section versus energy curve is consistent with experiment.…”

Section: Resultscontrasting

confidence: 64%

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

2003

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The relativistic distorted-wave Born approximation is used to calculate differential and total cross sections for inner shell ionization of neutral atoms by electron and positron impact. The target atom is described within the independent-electron approximation using the self-consistent Dirac-Fock-Slater potential. The distorting potential for the projectile is also set equal to the Dirac-Fock-Slater potential. For electrons, this guarantees orthogonality of all the orbitals involved and simplifies the calculation of exchange T-matrix elements. The interaction between the projectile and the target electrons is assumed to reduce to the instantaneous Coulomb interaction. The adopted numerical algorithm allows the calculation of differential and total cross sections for projectiles with kinetic energies ranging from the ionization threshold up to about ten times this value. Algorithm accuracy and stability are demonstrated by comparing differential cross sections calculated by our code with the distorting potential set to zero with equivalent results generated by a more robust code that uses the conventional plane-wave Born approximation. Sample calculation results are presented for ionization of K-and L-shells of various elements and compared with the available experimental data.

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Section: Resultscontrasting

confidence: 64%

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

2003

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“…We have recently shown [23] that measurements of the energy-dependence of K-shell ionization cross sections of Ni and Cu were in good agreement with the results of an optical-data model proposed by Mayol and Salvat [24]. This agreement motivated the extension of the study to other bound shells.…”

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confidence: 79%

Relative Cross Sections for L- and M-Shell Ionization by Electron Impact

et al. 2000

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Results from measurements and calculations of relative L-and M-shell ionization cross sections by electron impact are presented. Measurements were performed for elements Te, Au and Bi on an electron microprobe with specimens consisting of extremely thin ®lms of the studied element deposited on thin, self-supporting, carbon layers. The relative variation of the ionization cross section was obtained by counting the number of characteristic X-rays from the considered element and shell, for varying incident electron energies, from the ionization energy up to 40 keV. Measured data were corrected to account for the energy-dependent spread of the electron beam within the active ®lm and for the ionization due to the electrons backscattered from the carbon layer, using Monte Carlo simulation. Cross sections were evaluated in the Born approximation using an opticaldata model with numerically evaluated dipole photoelectric cross sections. Calculated ionization cross section were converted to vacancy production cross sections, which can be directly compared with our experimental data.Reliable cross sections for inner-shell ionization by impact of keV electrons are required for quantitative Auger electron spectroscopy (AES), electron probe microanalysis (EPMA) and electron energy loss spectroscopy (EELS). In spite of this need, simple systematic methods to calculate ionization cross sections from ®rst principles remain to be found. The usual practice consists in using semi-empirical formulae, which have limited ranges of validity and normally lead to signi®cantly different results. In the energy range considered here, 1 ± 50 keV, experimental measurements have been mostly carried out for Kshell ionization; cross section data for L-and M-shells are, unfortunately, very scarce. As far as we know, absolute L-shell ionization cross sections have been reported only for the elements P, S and Cl [1], Ar [2 ± 5], Kr [6], Xe [6,7] and Au [8 ± 11] (see also refs. [12,13]). Comprehensive reviews of experimental measurements (as well as theoretical calculations and semi-empirical formulae) of inner-shell ionization cross sections have been published by Powell [14,15,16]. Most of the reported cross sections were based on the measurement of characteristic X-rays which are emitted in the de-exitation of ionized atoms in the gas phase. Because of the lack of knowledge of the corresponding¯uorescence yields and CosterKronig decay yields, experimental results are affected by large uncertainties. Measurements using thick solid samples have also been performed, but the results are obscured by multiple scattering within the target. It is thus dif®cult to establish the reliability of semiempirical formulae and theoretical calculations by comparison with the available experimental data. This dif®culty is found not only regarding the absolute value of the cross section, but also for its energy dependence.The determination of the (relative) energy dependence of the ionization cross section is of interest for

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“…In order to perform a comparison with the analytical prediction for σ L i given by Campos et al it is necessary to choose a set of ω i . The predicted x-ray production crosssections lie between the present experimental data and those from [13]. The discrepancies between both sets of experimental data may be due to several reasons.…”

Section: Fluorescence Yieldscontrasting

confidence: 42%

Silver L₁, L₂and L₃cross-sections for ionization and x-ray production by electron impact

Sepúlveda

Bertol

Vasconcellos

et al. 2014

J. Phys. B: At. Mol. Opt. Phys.

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The experimental determination of ionization cross-sections and total x-ray production crosssections under electron impact is carried out for the three silver L-subshells. The very complex spectral structure involving several satellite bands was previously investigated by analyzing wavelength-dispersive spectra acquired in an electron microprobe. In this work, careful spectral processing is carried out by means of the POEMA software developed previously, considering the spectral energy intervals which include the main Ag-L emissions. The resulting ionization cross-sections are compared with analytical models based on distorted wave Born approximation calculations, the experimental determinations of the present work being underestimated by these predictions. To the best of the authors' knowledge, this is the first time these magnitudes are reported in the literature in this energy range. The total L-shell x-ray production cross-sections are also compared with the only previous experimental data found, obtained with different experimental settings.

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Measurements of absolute cross sections for K-shell ionization of Fe and Mn by electron impact

Cited by 25 publications

References 16 publications

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

Relative Cross Sections for L- and M-Shell Ionization by Electron Impact

Silver L₁, L₂and L₃cross-sections for ionization and x-ray production by electron impact

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Measurements of absolute cross sections for K-shell ionization of Fe and Mn by electron impact

Cited by 25 publications

References 16 publications

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

Distorted-wave calculation of cross sections for inner-shell ionization by electron and positron impact

Relative Cross Sections for L- and M-Shell Ionization by Electron Impact

Silver L1, L2and L3cross-sections for ionization and x-ray production by electron impact

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Silver L₁, L₂and L₃cross-sections for ionization and x-ray production by electron impact