X-ray Fluorescence Cross-sections For Elements Research Articles

Measurement of L XRF cross sections for elements with 33 ≤ Z ≤ 51 and their interpretation in terms of L (i = 1–3) subshell vacancy decay parameters

Abstract The Li (i = 1–3) subshell integral X-ray fluorescence (XRF) cross sections have been measured for 17 elements with 33 ≤ Z ≤ 51 following photoionization by the Mn K X-rays (EKαβ = 5.96 keV). The Li (i = 1–3) subshell X-rays were measured using a low-energy Ge (LEGe) detector at an emission angle, ψ = 125°, where angle-dependent emission effects, if any, are nullified as P2(cos ψ) ∼ 0. The XRF cross sections were interpreted in terms of available sets of theoretical Li (i = 1–3) subshell photoionization cross sections, radiative transition probabilities, and the atomic vacancy decay parameters, namely, fluorescence (ωi) and Coster-Kronig (fij) yields. A set of L1 subshell fluorescence (ω1) yields was deduced for the elements with 37 ≤ Z ≤ 51 from the present measured Lγ2,3,(4) [L1-N2,3(O2,3)] XRF cross sections. The ω1 values exhibit jumps at Z = 40 and 49, which are identified to be due to cut-off of the L1L2M4,5 and L1L3M4,5 Coster-Kronig (CK) transitions predicted by calculations based on relativistic Dirac-Hartree-Slater (RDHS) model. However, the measured ω1 values are found to differ considerably from those based on the RDHS model calculations for the elements below Z = 50. The pronounced discrepancies between measured and theoretical ω1 values are likely to be due to overestimation of the L1-L2,3M4,5 CK transition rates by a factor of ∼2–3. Our experiential results demand consideration of extra-atomic relaxation from the solid-state effects and exchange splitting in many-body theoretical calculations of the low-energy CK transitions.

Measurement of L X-ray fluorescence cross-sections for elements with 45 ⩽ Z ⩽ 50 using synchrotron radiation at 8 keV

The L shell fluorescence cross-sections of the elements in range 45 ⩽ Z ⩽ 50 have been determined at 8 keV using Synchrotron radiation. The individual L X-ray photons, Ll, Lα, Lβ I, Lβ II, Lγ I and Lγ II produced in the target were measured with high resolution Si( Li) detector. The experimental set-up provided a low background by using linearly polarized monoenergetic photon beam, improving the signal-to-noise ratio. The experimental cross-sections obtained in this work were compared with available experimental data from Scofield [1,2] Krause [3,4] and Scofield and Puri et al. [5,6]. These experimental values closely agree with the theoretical values calculated using Scofield and Krause data, except for the case of Lγ, where values measured of this work are slighter higher.

F-64 L Shell X-ray Fluorescence Cross-Sections for Elements with 33 ≤ Z ≤ 50

Accurate experimental data regarding the X-ray fluorescence (XRF) cross sections and fluorescence yields are important in basic studies of nuclear and atomic processes leading to the emission of X-ray and Auger electrons. The data is also required for many practical applications like elemental analysis by x-ray emission technique, dosimetric computation for medical physics and irradiation processes [1]. A systematic study of the Li (i =1-3) subshell x-ray fluorescence cross sections at the 5.89 keV photon energy has been undertaken for the elements in the atomic region 33  Z  50. The measurements have been performed under vacuum ~10 -2 torr using energy-dispersive spectrometer involving an LEGe (FWHM 150 eV at 5.895 keV) detector. The cross sections for the possible resolved L x-ray components were deduced and compared with those evaluated using the most reliable theoretical values of Li (i = 1, 2, 3) subshell photoionization cross sections, fluorescence yields, x-ray emission rates and Coster-Kronig transition probabilities [2]. For the L, L and L1,5 groups of x rays, the measured cross sections for all the elements are in agreement with theoretical cross sections. The measured L2,3 cross sections in the atomic region 39  Z  46 are in general agreement within ~10% except for 39Y, where the difference ~25% was observed. The comparison provides the insight regarding the cutoff energy of the L1-L2M4,5 and L1-L3M4,5 CK transitions at Z~39, and L1-L3M4,5 and L2-L3M4,5 CK transitions at Z ~50 as predicted by the RDHS model [2].

Experimental L x-ray fluorescence cross-sections for elements with 45 ≤Z ≤ 50 at 7 keV by synchrotron radiation photoionization

L x-ray fluorescence cross-sections for elements with 45 ≤ Z ≤ 50 were measured at 7 keV using synchrotron radiation photoionization. The experimental set-up provided a linearly polarized monoenergetic photon beam producing a low background and improving the signal-to-noise ratio. The data obtained for the L lines, Ll, Lα, LβI, LβII, LγI and LγII, were grouped considering the transition scheme, the energies of the emission lines and the detector resolution. Results for the experimental cross-sections obtained were compared with theoretical values using two different data tables. In general, it was found that the experimental fluorescence cross-sections are slightly higher (7–10%) than the theoretically calculated data and in some cases these differences are up to 40%. Copyright © 2005 John Wiley & Sons, Ltd.

Generation of experimental L x‐ray fluorescence cross‐sections for inter‐elements at inter‐energies EL1 ≤ E ≤ EK (computer program IGELCS)

AbstractThe experimental values of L x‐ray fluorescence (XRF) cross‐sections are not available for all the elements in the range La–U, at all the photon energies E in the range EL1 ≤ E ≤ EK. To generate L XRF cross‐sections, where experimental measurements are not available, two empirical relations have been developed, one between the L XRF cross‐sections and photon energy and the other between the L XRF cross‐sections and atomic number. For the measured data on L XRF cross‐sections at incident energies between Ll and K edges of an element and the data on L XRF cross‐sections for elements in the range 57 ≤ Z ≤ 92 at an energy value, polynomial fits have been derived. The L XRF cross‐section values generated with the derived empirical relations were found to be in agreement with the experimental values within their experimental uncertainties. Subsequently, a software code IGELCS was developed to interpolate and to generate the cross‐sections at inter‐energies and for inter‐elements in a single computer run. The running of the software requires minimum input data on five elements at five common energies. Copyright © 2003 John Wiley & Sons, Ltd.

Variation of K X-Ray Fluorescence Cross-Sections for Elements in the Range 22 ≤ Z ≤ 29 at Various Energies

Abstract K X-ray fluorescence cross-sections were experimentally determined for elements in the range 22 ≤ Z ≤ 29 at various energies using secondary excitation method. K X-rays emitted by samples were counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. Obtained values were compared with the calculated values. The experimental values are systematically higher than the theoretical values.

Hf, Ta, W and Re experimental L X-ray fluorescence cross-sections at 12, 13 and 14 keV with synchrotron radiation

Experimental determinations of L X-ray fluorescence cross-sections for elements with 72≤Z≤75 at 12, 13 and 14 keV were carried out with synchrotron radiation. The experimental set-up provided a linearly polarized monoenergetic photon beam producing a very low background, which improved the signal-to-noise ratio and reduced the experimental uncertainties. Results of the experimental cross-sections obtained for the L lines were grouped considering the transitions scheme, the energies of the emission lines and the detector's resolution. The data obtained were compared with theoretical ones using two different data tables. A very good agreement was found between our experimental values and the theoretical values calculated using Puri's data (X-Ray Spectrom. 22 (1993) 358–361).

L X-ray fluorescence cross-sections for rare earths at 10 and 11 keV with synchrotron radiation

Experimental determinations of L X-ray fluorescence cross-sections for elements with 64⩽ Z⩽70 at 10 and 11 keV were carried out with synchrotron radiation. The experimental set-up provided a linearly polarized monoenergetic photon beam producing a very low background, which improved the signal-to-noise ratio and reduced the experimental uncertainties. Results of the experimental cross-sections obtained for the L lines were grouped considering the transitions scheme, the energies of the emission lines and the detector's resolution. The data obtained were compared with theoretical ones using two different data tables. A very good agreement was found between our experimental values and the theoretical values calculated using Puri's data. A new set of ω L1 ,f 12 and f 13 coefficients was also used to calculate theoretical cross-sections for Gd. These theoretical cross-sections and our experimental values are in excellent agreement.

Rare earth experimental L x‐ray fluorescence cross‐sections at 13 and 14 keV with synchrotron radiation

AbstractExperimental determinations of L x‐ray fluorescence cross‐sections for elements with 64 ≤ Z ≤ 70 at 13 and 14 keV were carried out with synchrotron radiation. The experimental set‐up provided a linearly polarized monoenergetic photon beam producing a very low background, which improved the signal‐to‐noise ratio and reduced the experimental uncertainties. Results of the experimental cross‐sections obtained for the L lines were grouped considering the transitions scheme, the energies of the emission lines and the detector's resolution. The data obtained were compared with theoretical data using two different data tables. Very good agreement was found between our experimental values and the theoretical values calculated using Puri et al.'s data. A new set of ω1, f12 and f13 coefficients for Gd were also used to calculate theoretical cross‐sections and the experimental values were in excellent agreement. Copyright © 2001 John Wiley & Sons, Ltd.

L X-ray fluorescence cross-sections for elements 40≤ Z≤92 at energies 2–116 keV (a computer program ‘LCSGEN’)

L ℓ,L α ,L β and L γ X-ray fluorescence cross-sections for the elements 40≤ Z≤92 at energies 2–116 keV have been generated from an empirical relation fitted to two sets of available semi-empirical and theoretical cross-sectional values. The excitation energy E for an element is constrained by the condition that only L and higher shell vacancies are produced in the element. The closeness of generated and existing values of L X-ray fluorescence cross-sections recommends the use of generated values in the fields of Atomic & Molecular Physics and trace elemental analysis. For this purpose a computer software ‘LCSGEN’ has been developed. On personal computer ‘LCSGEN’ generates the cross-sectional values in b/atom just by entering the atomic number of element and excitation photo energy in keV.