L-subshell X-ray Production Research Articles

Au L-shell x-ray emission induced by 154.3–423.9 MeV/u C6+ ions

The L-shell x-ray emissions of gold are investigated for the bombardment of high energy C6+ ions in the high energy region of 154.3–423.9 MeV/u. Due to the multiple ionization of outer-shell electrons at the movement of L x-ray emission, the blue shift of the experimental x-ray energy and an enhancement of the relative intensity ratios of Lι, Lβ–Lα x rays are observed. Using the improved thin target formula and considering the effect of multiple ionization on atomic parameters, the L-subshell x-ray production cross sections are extracted from the counts and compared with the theoretical estimations of BEA, PWBA and ECPSSR. It is found that the relative corrections of ECPSSR on PWBA can be ignored in the present experimental energy region. The calculations of PWBA and ECPSSR are almost identical and both are larger than the experimental results. The BEA is in better agreement with the experiment as a whole.

Measurements of L-subshell x-ray production cross sections and M-shell x-ray yields of Pb by low-energy electron impact using the thick-target method

The Lα, Lβ, and Lγ x-ray production cross sections and M-shell x-ray yields by 5–29 keV electrons bombarding a thick Pb target were measured. The effects of multiple-scattered electrons, from the bremsstrahlung and other secondary particles within the thick sample were corrected using the Monte Carlo simulations. The experimental results are compared with the DWBA predictions of Bote et al., and also with the experimental data from the literature. The results indicate that the measurements of the production cross sections for the L subshells of the elements with higher atomic numbers using the thick-target method are feasible and reliable.

Measurement of L X-ray production cross sections of Ce, Nd, Sm, Eu, Gd, and Dy by impact of 9Be2+ ions with energies in the interval 5.25 MeV to 6.75 MeV

Abstract Measurements of L-subshell X-ray production cross sections from Ce, Nd, Sm, Eu, Gd, and Dy, induced by the irradiation with 9Be2+ ions having energies between 5.25 MeV and 6.75 MeV are presented, with the purpose of comparing them with theoretical predictions from the ECPSSR model with exact integration limits, known as eCPSSR. Adjustments to this theory due to Multiple Ionization and Electron Capture were also considered. It is not possible to determine which of the theoretical models better describes the experimental results, because of their similar predictions.

A Scaling Law for L-Shell X-Ray Production Cross Sections Induced by Impact of 4He+, 9Be2+, and 14N2+ Ions

Experimental results of L-subshell X-ray production cross sections induced by the impact of several ions heavier than protons were compiled in order to propose possible scaling laws. The ions of interest in this work are 4He+, 9Be2+, and 14N2+. A feasible universal scaling for the x-ray production cross sections of the Lα (L3M4 + L3M5) line is based on a reduced velocity parameter ξRL1,2. In this scheme, the experimental data follow well resolved curves for each ion. A similar scaling for the Lγ line (L2N4 + L1N2 + L1N3+ L1O3 + L1O2 + L2N1 + L2O4) is also recommended, based on a different reduced velocity parameter ξRL1,2. These results appear to be useful for all the studied projectile-target combinations covered in this work, supporting the idea that more theoretical studies in this direction should be done. However, the behavior of the fitting does not seem to follow the previously observed one.

New data base for Lα, Lβ, Lγ x-ray production by protons, new empirical fits, extraction of L-subshell ionization cross sections with various atomic parameters, and their comparison with the ECPSSR theory and its modifications: a recommendation for reliable choice of atomic parameters and ionization theory for PIXE analysis

Tables of L-shell and L-subshell x-ray production cross sections by protons from 1994 are updated, and the so constructed data base is fitted to formulas for empirical Lα, Lβ, Lγ x-ray production cross sections. Based on these fits, empirical L-subshell ionization cross sections are generated with various sets of atomic parameters with and without alteration for multiple ionizations. The extracted ionization cross sections are compared with the predictions of the ECPSSR theory and it modifications. Based on comparisons with different choice of the atomic parameters and theories, we will recommend an optimal combination of the atomic parameters and ionization theory for a reliable input in PIXE applications software.

Study of the L-subshell X-ray production cross sections of Au by 20—50 MeV O5+ bombardments

The experiments were performed at HI-13 tandem accelerator at the Chinese Institute of Atomic Energy （CIAE）, in which the L-shell X-ray relative production cross section was measured for solid targets Au bombarded by 20—50 MeV O5+ions. The ratios of Au L-subshell production cross sections σ（Lβ）/σ（Lα），σ（Lγ）/σ（Lα），σ（Ll）/σ（Lα） have been calculated according to the experimental data. The results are compared with the predictions of the ECPSSR theory. Reasonable agreement between theory and experiment was obtained.

Proton induced L and L-subshell X-ray cross-sections in Sm and Yb at 1–2.5 MeV

L and L-subshell X-ray production cross-sections for protons on Sm and Yb have been measured in the incident energy range of 1–2.5MeV. The values obtained agree with data available in Sokhi and Crumpton [R.S. Sokhi, D. Crumpton, At. Data Nucl. Data Tables 30 (1984) 49] and Orlic et al. [I. Orlic, C.H. Sow, S.M. Tang, At. Data Nucl. Data Tables 56 (1994) 159] and the uncertainties are less than 12%. The data are compared with predictions of the modified plane wave Born approximation by introducing corrections for energy loss (E), Coulomb deflection (C), perturbed stationary state (PSS) and relativistic (R) effects which is the so-called ECPSSR model.

Relative L-shell X-ray emission rates in PIXE

L shell X-ray emission rates usually used as a part of a data base for analysis of PIXE spectra are theoretical values based on Dirac-Hartree-Slater (DHS) [J.H. Scofield, At. Data Nucl. Data Tables 14 (1974) 121] or Dirac-Hartree-Fock (DHF) [J.H. Scofield, Phys. Rev. A 10 (1974) 1507] calculations, or semiempirical data of Salem et al. [At. Data Nucl. Data Tables 14 (1974) 91], obtained from pre-1974 experiments with radioactive sources or sources ionized by photon or electron bombardment. Recently published L-subshell X-ray production cross sections by proton impact have been used to extract relative L-shell X-ray emission rates for some groups of L-shell X-ray lines, in order to compare them with the values from the three data bases mentioned before.

L-subshell X-ray production by 400–700 keV protons in selected elements with 52 ≤ Z ≤ 71

The L-shell X-ray production cross section for proton impact of thin film targets of some elements with 52 ≤ Z ≤ 71 have been measured in the energy range 400–700 keV. Corrections due to proton stopping and X-ray attenuation in the films are taken into account. Experimental results are compared with the ECPSSR theory using the relativistic reduced proton velocity ξLiR. The Lα line is also compared with a semiempirical function based on a fit to the ratios of published experimental data with the ECPSSR predictions. Present experimental results are higher than the theoretical predictions, in accordance with previous results, except for the Lγ2,3 line, for which the results are lower.

Measurement of Ll, L alpha, L beta, and L gamma x-ray production cross sections in rare-earth elements by 60-keV photons.

Our earlier measurements [Shatindra, Allawadhi, and Sood, Phys. Rev. A 31, 2918 (1985)] of Ll, L\ensuremath{\alpha}, L\ensuremath{\beta}, and L\ensuremath{\gamma} x-ray production cross sections in elements with 73\ensuremath{\le}Z\ensuremath{\le}92 by 60-keV photons have been extended to 11 rare-earth elements in the range 57\ensuremath{\le}Z\ensuremath{\le}68 in order to examine enhancement in L-subshell x-ray production due to transfer of vacancies from the K to the L shell. The measured values of absolute cross sections have been interpreted in terms of K-shell photoelectric cross sections, probabilities of K\ensuremath{\rightarrow}L radiative and nonradiative transitions, L-subshell photoelectric cross sections, fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates. Fairly good agreement between the experimental and calculated values indicates indirectly the correctness of the theoretical calculations of the atomic parameters in terms of which the experimental results have been interpreted.

Increased-binding effects in the L-subshell ionization of Nd, Gd, and Er by charged particles

L-subshell X-ray production cross sections of Nd, Gd and Er for incident deuterons (0.30–1.00 MeV) and α particles (0.60–2.00 MeV) were measured using standard techniques. It is possible to isolate the Coulomb-deflection and increased-binding effects (which are a part of the perturbed stationary state (PSS) theoretical treatment of these phenomena) by forming ratios of the production cross sections for equal velocity pairs of incident particles (deuterons and protons for the Coulomb-deflection effect, α particles and deuterons for the increased-binding effect). The PSS theory provides a good fit to the experimental results for the Coulomb-deflection effect for all three Subshells for these same three elements [L.A. Rayburn, Nucl. Instr. and Meth. B40/41 (1989) 113]; however, it does not provide a good fit for the increased-binding effect.

L-subshell ionization of Dy and Ho by 0.4–3.0 MeV protons

L-subshell X-ray production cross sections of Dy and Ho were measured for incident protons with energies of 0.4–0.3 MeV. Subshell ionization cross sections and their ratios are compared with the predictions of the ECPSSR theory [1].

Coulomb-deflection effects in the L-subshell ionization of Nd, Gd and Er by charged particles

L-subshell X-ray production cross sections of Nd, Gd and Er for incident protons (0.25–1.00 MeV) and deuterons (0.40–2.00 MeV) were measured using standard techniques. It is possible to isolate the Coulomb-deflection effect (which is a part of the perturbed stationary state (PSS) theoretical treatment of this phenomenon) by forming ratios of the production cross sections for equal-velocity pairs of particles. The PSS theory provides a good fit to the experimental results for all three subshells.

Low-velocity effects in L-subshell ionisation of Ta and W induced by proton, deuteron and alpha impact

L-subshell X-ray production cross sections were measured for Ta and W bombarded by 0.20 to 0.90 MeV u-1 protons and deuterons and by 0.2 to 0.45 MeV u-1 alpha particles. Lalpha Lgamma 1 and Lgamma 2,3 lines were selected to convert X-ray production cross sections into ionisation cross sections. The deuteron to proton-induced cross section ratios show that the Coulomb and energy loss effects are well accounted for in all subshells. The alpha to deuteron-induced cross section ratios show that the theory overcorrects the binding effect, the theoretical ratios being lower than the experimental ones by roughly 25% for the L3 subshell and 75% for the L2 subshell. It is argued that this difference between the ratios, and the poor agreement on the L2-subshell absolute cross sections, may be accounted for by assuming a 10-20% deviation in the values used for the fluorescence and Coster-Kronig yields and for the emission rates; such a deviation may be induced by the projectile.

L-subshell X-ray Production by 100?250 keV/a.m.u. Ions

Individual L-subshell ionization cross sections have been measured for bombardment of 100-200 keY H+ ions in 10 keY steps upon a thick Gd (Z = 64) target and for bombardment of 600-1000 keY He+ ions in 100 keY steps upon thick W (Z = 74) and thick and thin Au (Z = 79) targets. Experimental results for the individual L subshells are compared with the theoretical predictions of the ECPSSR theory as developed by Brandt and Lapicki. The differences are discussed as a function of the reduCi:,d ion velocity. The occurrence of collision induced intra-shell transitions is discussed as a possible source for the discrepancy between experiment and theory.

L-Subshell X-Ray Production Cross Sections of Ba, La and Ce for Proton Energies from 0.25 to 2.00 MeV

Protons from the University of Texas at Arlington's 2 MV Van de Graaff accelerator were used to produce characteristic L x-rays from thin targets of Ba, La and Ce. The incident proton energy was varied from 0.25 to 2.00 MeV. The x-rays were detected by a detector mounted at 90° to the incident beam direction. Measured x-ray production cross sections were converted to ionization cross sections by the use of subshell fluorescence yields and Coster-Kronig transition probabilities taken from Bambynek. Inflection points are found in the L1-subshell ionization cross section for all three elements. Although the theoretical plane-wave Born approximation (PWBA) curves do have inflection points (whereas the binary encounter approximation (BEA) curves do not), the PWBA theory does not correctly predict the proton energies at which these occur for all three elements.