Measurements Of X-ray Production Cross Sections Research Articles

Semi-empirical parameterization of HI/p L-shell X-ray production cross section ratios in Bi for Heavy Ion PIXE

Quantitative analysis of materials from Heavy Ion PIXE spectra remains impeded by the lack of reliable X-ray production cross section (XPCS) data. Although efforts at experimental Heavy Ion induced XPCS measurements still continue, Multiple Ionisation (MI) effects, which are not fully described by theory, render simulations of heavy ion PIXE data unreliable for large Z1/Z2 collisions, especially at low energies. This is also exacerbated by the random selection of projectile-target combinations for measured and reported experimental data available to validate theory. This study explored heavy ion induced X-ray production cross section deviations from those induced by protons at the same ion velocity. This enabled evaluations of the degree to which cross sections are enhanced through MI effects, with the aim of predicting XPCS due to heavy ion impact. The evaluation was carried out through the scaling of experimental heavy ion to theoretical proton cross section ratios (R), which were then used for the interpolation of XPCS in the same target element for ‘missing’ projectiles within the range of evaluation. Here we present measurements of heavy ion induced total L-shell XPCS in Bi, carried out to determine HI/p MI induced deviations due to C, F, Cl and Ti projectiles at an ion velocity range of (0.2–1.0) MeV/nucleon.

Measurement of L-shell X-ray production cross sections in 89Y, 158Gd and 209Bi due to 0.3 MeV/u – 1.0 MeV/u 12C ions

Experimental heavy ion induced X–ray production cross sections in matter continue to be of importance for both fundamental ion-atom collision studies as well as practical applications such as in nuclear analytical techniques. This work presents results of L-shell X-ray production cross section measurements in 89Y, 158Gd and 209Bi due to 4 MeV–12 MeV 12Cq + projectile ions. Experimental data are compared with theoretical calculations based on the ECPSSR, ECPSSR + EC and ECPSSR-UA models. Data show fairly good, albeit energy dependent agreement with the different models for yttrium and gadolinium cross sections. For bismuth, all three models overestimate data by an almost constant factor of two. The effect of multiple ionization on the l-line intensity ratios is also presented for gadolinium and bismuth targets.

L- and M-shell X-ray production cross section measurements in 73Ta and 78Pt using B3+,4+-ions of energies below and above the potential barrier

In this paper, we report the L- and M-shell X-ray production cross sections in 73Ta and 78Pt caused by the bombardment of 35 to 60 MeV B3+,4+-ions. The energies of B-ions, below and above the potential barrier, were selected to study the effect on inner- and outer-shell ionization i.e. absolute X-ray production cross sections for various L- and M X-ray lines/group of lines (namely Lℓ, Lα2, Lα1, Lη, Lβ4,6, Lβ1, Lβ3, Lβ2,15, Lβ5,7,9,10, Lγ5, Lγ1, Lγ2,3,6, Lγ4,4′, Mξ2,1, Mδ + M3N1, Mα1,2 + M2N1, Mβ + Mη, Mγ, Mm11 (M3O1 + M3O4,5), Mm12 (M2N4 + M1N3), Mm21 (M2O1), Mm22 (M2O4 + M1O2,3) and the change in the intensity ratios due to multiple ionization of M- and higher-shells. The present measurements were carried out at 16UD Pelletron Accelerator at Inter-University Accelerator Centre (IUAC) Delhi. The ion beams were bombarded on thin targets evaporated on an ultrapure carbon backing of 10 μg/cm2. The targets fixed on a steel ladder were placed in an evacuated (<10−6 Torr) scattering chamber at 45° each to the beam direction and to the Si(Li) detector. The recorded L and M X-ray spectra were separately deconvoluted into various components of the L and M X-ray lines using the computer code after subtracting suitable background. The experimental results have been compared with the theoretical values by converting the L and M-subshell ionization cross sections based on the PWBA and ECPSSR direct-ionization theories taking into effect the sub-shell fluorescence yields, Coster-Kronig transition probabilities and transition rates based on Dirac-Fock and Dirac-Hartree-Slater models. In the present measurements (0.0641 ≤ Z1/Z2 ≤ 0.0685), the velocity ratios v1/v2pi and the reduced ion velocity ξpi = 2v1/(θpi.v2pi) for p = L- or M-shell are in the range of 0.309 ≤ v1/v2Li ≤ 0.435 and 0.913 ≤ ξLi ≤ 1.316 and the ratios v1/v2Mi and ξMi for M-shell are in the range of 0.555 ≤ v1/v2Mi ≤ 0.790 and 2.575 ≤ ξMi ≤ 3.779 respectively. To the best of our information, this study of B-ion impact on 73Ta and 78Pt, near the potential barrier of the system which falls in the fast (ξLi ≈ 1, ξMi > 1) collision regime, is being reported for the first time.

Heavy ion PIXE cross sections in Ti, Zn, Nb, Ru and Ta for 4.8–30.0 MeV oxygen and 3.0–12.0 MeV lithium beams

Heavy ion Particle Induced X-ray Emission (PIXE) spectroscopy offers a number of advantages over standard proton PIXE, such as higher yields and therefore higher sensitivity. However, in order to be able to use heavy ion PIXE more detailed measurements of the ionisation and X-ray cross sections for heavy ions are required. This issue was recognised by one of the Coordinated Research Projects (CRP) of the IAEA on MeV Secondary Ion Mass Spectrometry (SIMS). ANSTO took part in this CRP and we measured X-ray production cross sections on a range of samples for oxygen and lithium beam in the energy range of 4.8–30 MeV and 3–12 MeV, respectively. Here we report on these X-ray production cross section measurements and compare the results with theoretical models. Further energy shifts of the characteristic X-ray lines for the different ion-target combinations are presented and discussed.

Measurement of X-ray production cross-sections of Ti, V, Cr, Mn, Fe, Co, Ni and Cu molecules

K shell X-ray production cross-sections in the Ti, V, Cr, Mn, Fe, Co, Ni, and Cu in the molecules were studied at 59.5 keV excitation energy by using a Si(Li) detector ( FWHM = 155 eV at 5.96 keV). The present results are compared with other theoretical values.

Experimental measurements of X-ray production cross-sections by protons of energies between 1 and 2.3 MeV and comparison with theoretical predictions of PWBA and ECPSSR models

Considering the importance of the X-ray production cross-sections for the determination of element concentrations in a given material, we have measured them experimentally for the elements Al, Cu and In using proton beams of energy between 1 and 2.3 MeV. The X-ray production cross-sections obtained are compared with the previous experimental cross-sections reported by H. Paul, J. Sachert [Atomic Data and Nuclear Data Tables 42 (1989) 105] and our calculations by PWBA [E. Merzbacher, H. Lewis, Encyclopédia of Physics (1958) 166] (plane wave born approximation) and ECPSSR [W. Brandt, G. Lapicki, J. Phys. B 9 (1976) 1203] (based on PWBA model incorporating corrective effects). Our experimental results are in good agreement with the published experimental results of H. Paul, J. Sachert [Atomic Data and Nuclear Data Tables 42 (1989) 105] and even with a small error for Al target. Our results agree also well with theoretical predictions of PWBA and ECPSSR models. But at low energies PWBA calculations overestimate the cross-section values. The introduction of corrective effects in the ECPSSR model has removed this disagreement.

Measurement of the anisotropy parameters for the M X-rays of gold induced by 3–9 MeV carbon ions

The angular distribution of Au M X-rays induced by 3–9 MeV carbon ions has been measured with a Si(Li) detector and found to be strongly anisotropic. The measured values of the anisotropy parameters range between 10% and 38%. The implication of such high values of the anisotropy parameter for M X-ray production cross section measurements has been discussed.

M-shell x-ray production cross section measurements in Pb and Bi due to the impact of protons and nickel ions

M-shell x-ray production cross sections in Pb have been measured using 58 - 82 MeV ions and those in Bi by 1 - 5 MeV protons and 58 - 82 MeV ions (q = 5, 6). The experimental results have been compared with the predictions of the plane-wave Born approximation (PWBA) and with the calculations of the perturbed stationary state theory (ECPSSR) accounting for the energy loss (E), Coulomb deflection (C) and relativistic (R) effects. The present results of proton impact on bismuth have also been compared with the experimental data available from other investigations. To the best of our knowledge, the M-shell x-ray production cross sections in Pb and Bi by Ni-ion impact are reported here for the first time. Good agreement of the present results with the predictions of the ECPSSR theory has been observed for the total M x-ray cross sections in Bi due to proton impact while discrepancies to a factor of 1.5 - 2.5 in the case of total M x-ray cross sections have been observed between the present experimental and theoretical (PWBA and ECPSSR, respectively) results for Pb and Bi in the case of Ni-ion impact. These discrepancies between the experimental and theoretical results could be attributed to the effect of multiple ionization on the x-ray emission probabilities. If the modified value of the average fluorescence yield accounting for the outer-shell multiple ionization is used, the theoretical results of total M-shell x-ray cross sections based on the PWBA theory show fair agreement with the experimental results (within experimental uncertainties) while the ECPSSR theory is found to underestimate the experimental results by about 40% for both Pb and Bi in the case of Ni-ion impact. Furthermore, the and x-ray cross sections have been evaluated experimentally for both Pb and Bi. The comparison of these results with the corresponding theoretical estimates have been done only for Pb as the emission rates for various M x-ray transitions of Bi are not available in the literature. The comparison of the cross sections show fair agreement with the PWBA-based theoretical values, while there are discrepancies of a factor of 10 and 20 in the cases of and x-ray transitions.

Absolute CKx-ray production cross sections for 18-26-MeV protons on thin carbon foils

Absolute C K x-ray production cross-section measurements using 18--26-MeV protons on thin carbon foils extend the range of previous measurements in the asymptotic region. These measurements permit extraction of the two main parameters of the asymptotic theory, viz., M/sup 2//sub tot/ = 0.84 and C/sub tot/ = 8.2, which are in good agreement with those obtained in previous work at lower energies. The ionization cross sections extracted from these measurements are compared with the predictions of the asymptotic theory as well as the binary-encounter, semiclassical, and plane-wave Born approximation theories.