J. Braziewicz

Trace element load in cancer and normal lung tissue

Abstract Samples of malignant and benign human lung tissues were analysed by two complementary methods, i.e., particle induced X-ray emission (PIXE) and total reflection X-ray fluorescence (TRXRF). The concentration of trace elements of P, S, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Se, Sr, Hg and Pb was determined in squamous cancer of lung tissue from 65 people and in the benign lung tumour tissue from 5 people. Several elements shows enhancement in cancerous lung tissue of women in comparison to men, i.e., titanium show maximum enhancement by 48% followed by Cr (20%) and Mn (36%). At the same time trace element concentration of Sr and Pb are declaimed by 30% and 20% in women population. Physical basis of used analytical methods, experimental set-up and the procedure of sample preparation are described.

Some aspects of statistical distribution of trace element concentrations in biomedical samples

Concentrations of trace elements in biomedical samples were studied using X-ray fluorescence (XRF), total reflection X-ray fluorescence (TRXRF) and particle-induced X-ray emission (PIXE) methods. Used analytical methods were compared in terms of their detection limits and applicability for studying the trace elements in large populations of biomedical samples. In a result, the XRF and TRXRF methods were selected to be used for the trace element concentration measurements in the urine and woman full-term placenta samples. The measured trace element concentration distributions were found to be strongly asymmetric and described by the logarithmic–normal distribution. Such a distribution is expected for the random sequential process, which realistically models a level of trace elements in studied biomedical samples. The importance and consequences of this finding are discussed, especially in the context of comparison of the concentration measurements in different populations of biomedical samples.

L-subshell ionization of rare earth elements by carbon ion bombardment

Measurements of L-shell X-ray production cross sections and corresponding L-subshell ionization cross sections for selected rare earth elements (57<or=Z<or=68) have been performed for 12C and 13C ion impact with energies 0.4-2.8 MeV amu-1. The influence of target thickness and projectile charge state on L-subshell ionization is examined experimentally. The measured L-subshell ionization cross sections are compared with the predictions of the ECPSSR and SCA theories. Strong underestimation of the experimental data in the low energy range by both theories is caused by the second-order effects not accounted for in the theoretical description. An agreement of the data with the theoretical predictions is improved by using the united atom limit for the effective binding energies.

M-SHELL X-RAY PRODUCTION CROSS SECTIONS FOR PIXE APPLICATIONS

M-shell X-ray production cross sections by protons of energies 0.1–4.0 MeV are reported for the most intense Mαβ(M4,5N6,7), Mγ(M3N4,5) and M3O4,5 M-X ray transitions appearing in PIXE spectra. The cross sections have been measured systematically for selected heavy elements between Ta and Th (Z2=73–90). Measured M-X-ray production cross sections were found to be universal with respect of M-shell scaled velocity ξM. The data are compared with available theoretical calculations of M-shell ionization by charged particles based on the plane-wave Born approximation (PWBA) and the semiclassical approximation (SCA), as well as the ECPSSR theory and relativistic RPWBA-BC which are going beyond the first order treatment. Simple parameterization of experimental proton induced M-X-ray cross sections is proposed for PIXE applications. This parameterization, being accurate within ±5%, can be used for precise determination of heavy metal concentrations by PIXE technique.

M-shell X-ray production in heavy elements by low-energy protons

Measurements of M-shell X-ray production cross sections in selected heavy elements (73 ≤ Z2 ≤ 90) have been performed for proton impact of energy 0.1–0.6 MeV. X-rays were collected by a Si(Li) detector, carefully calibrated for low-energy efficiency, and they were normalized to the projectiles that were elastically scattered into the surface barrier detector. The measured M-X-ray production cross sections are compared with the predictions of the first Born approximation, the semiclassical approximation, and the ECPSSR theory which corrects for energy loss, Coulomb deflection, binding-polarization and relativistic effects. The comparison of the present data with our earlier measurements and the data reported by other authors is discussed in detail. Strong underestimation (up to a factor of about 5) of experimental data by the ECPSSR theory is observed for the lowest energies.

The role of multiple ionization and subshell coupling effects in L-shell ionization of Au by oxygen ions

The ionization of L-subshell electrons in gold by the impact of 0.4-2.2 MeV amu-1 O ions was studied by observing excited Lγ(L-N, O) x-rays. We demonstrate that both the multiple ionization in outer M- and N-shells as well as the coupling effects in the L-shell play an important role in understanding the measured L-subshell ionization cross sections. The multiple ionization was found to be important in two aspects: first, the analysis of x-ray energy shifts and line broadening was crucial for proper interpretation of measured x-ray spectra; second, the additional vacancies in the M- and N-shells substantially influenced the L1-subshell fluorescence and Coster-Kronig (CK) yields, mainly by closing strong L1-L3M4,5 CK transitions. The data are compared with the simplified coupled-channels calculations using the `coupled-subshell model (CSM) based on the semiclassical approximation (SCA), which describes both direct Coulomb ionization as well as the L-subshell couplings within the same theoretical approach. A good agreement of the present data with the theoretical predictions based on the discussed SCA-CSM approach is observed. Present findings partly explain the long-standing problem of inadequate theoretical description of L-shell ionization by heavy ion impact.

MULTIPLE IONIZATION OF M- AND N-SHELLS IN HEAVY ATOMS BY O, SI AND S IONS

Abstract Multiple ionization in M- and N-shells in solid Au, Bi, Th and U targets was studied for O, Si and S ions of energies 0.4–2.0 MeV/amu. L γ X-rays measured with semiconductor Si(Li) detector were analysed by using a newly developed method of the simultaneous determination of X-ray energy shifts and line broadening caused by the multiple ionization in outer shells. In this approach both X-ray energy shifts and widths are expressed in terms of ionization probabilities and calculated energy shifts per vacancy, allowing thus the unique fitting of the L γ X-rays and determination of ionization probabilities. Derived ionization probabilities for M- and N-shells exhibit universal scaling predicted by the geometrical model (GM) for the ionization probabilities at the zero impact parameter. The influence of time evolution of the vacancies formed in M- and N-shells by ion impact is discussed.

L-subshell ionization by 14N ions

Abstract L-subshell ionization cross sections for selected heavy elements between La and Au were measured for 14N ions in the energy range 1.75–22.4 MeV. The L-X-ray yields were corrected for a substantial projectile energy-loss in the target, being up to 20% for the lowest energies, and the X-ray absorption effect. The measured L-subshell ionization cross sections are compared with the predictions of the ECPSSR theory for direct ionization and electron capture processes and the SCA calculations for direct ionization. Both theories underestimate the data for L2-subshell for the lowest energies. This is attributed to the effect of intra-shell transitions not accounted for in both calculations. Systematic overestimation of measured L3-subshell cross sections by the theories is also found for higher scaled velocities ξ > 0.5, where the binding-polarization effects are expected to play an important role.

Proton-induced L-shell X-ray production cross sections and their ratios

Thin targets of Sb, Te, Ho, Ta, W, Pt and Bi have been employed and L X-ray yields have been measured as a function of proton energy from 1.5 to 3.8 MeV. From these measurements the individual and total X-ray production cross sections and their ratios have been calculated and compared with the experimental results reported by other authors and with the perturbed stationary-state plane-wave Born approximation with correction for Coulomb deflection, relativistic and energy-loss effects resulting in the ECPSSR theory of Brandt and Lapicki (1979, 1981).

M-X-ray production cross-sections for 0.2–2 MeV deuterons

Abstract M-X-ray production cross-sections by deuterons of energies 0.2–2.0 MeV were measured systematically for selected heavy elements between Ta and Th and the results are reported for the most intense M αβ (M 4,5 N 6,7 ), M γ (M 3 N 4,5 ) and M 3 O 4,5 M-X-ray transitions. The measured M-X-ray production cross-sections are found to be universal with respect to M-shell scaled velocity ξ M , allowing thus a simple parameterization of the experimental deuteron-induced M-X-ray cross-sections for applications. This parameterization is found to be accurate within a few percent. The measured M-X-ray cross-sections for deuterons are compared with available theoretical calculations of M-shell ionization by charged particles.