L. Demir

Kα and Kβ X-ray fluorescence cross-sections in the atomic region 26⩽Z⩽42 excited by 59.5 keV photons

Abstract The Kα and Kβ X-ray fluorescence (XRF) cross-sections were experimentally determined for elements in the range 26⩽ Z ⩽42. The obtained experimental results were in good agreement with the theoretical values.

The polarization of X-rays and magnetic photoionization cross-sections for L3 sub-shell

The alignment of atoms with inner-shell vacancies resulting from ionization by photons was investigated by measuring the anisotropic emission of L shell X-ray lines. The X-ray line intensities were measured using an Si(Li) detector and radioisotope photon source in various emission angles. It was observed from measured intensities that Lalpha and Ll X-ray intensities for the L(3) sub-state depended on the emission angle, meaning that Lalpha and Ll X-rays had an anisotropic spatial distribution. Thus, the Lalpha to Ll intensity ratios for a set of elements were determined and alignment parameters for each element were obtained using these ratios. Also, the empirical values of the L(3) magnetic sub-state photoionization cross-sections for m(j)=3/2 and 1/2 were evaluated using the determined alignment parameters, sub-state photoionization cross-sections and the Coster-Kronig transition probabilities.

Measurement of angular dependence of photon-induced differential cross-sections of M X-rays from Pt, Au and Hg at 5.96 keV

Abstract The differential cross-section for the emission of M shell fluorescence X-rays from Pt, Au and Hg by 5.96 keV photons at seven angles ranging from 50° to 110° have been measured. The differential cross-section is found to decrease with increase in the emission angle, showing an anisotropic spatial distribution of M shell fluorescence X-rays. The present results contradict the predictions of Cooper and Zare (Cooper, J., Zare, R.N., 1969. Atomic Collisions Processes, vol. XIC. Gordon and Breach, New York. p.317) that after photoionization of inner shells, the vacancy state has equal population of magnetic substates and that the subsequent X-ray emission is isotropic, but confirm the predictions of the calculations of Flugge, Mehlhorn and Schmidt that the atomic inner-shell vacancies produced after photoionization are aligned and X-ray emission from the filling of vacancies in states with J >1/2 is anisotropic. The vacancies were created by the 5.96 keV γ-rays from an 55 Fe source and the M X-rays were measured using a Si(Li) detector.

Monte Carlo Calculations of XRF Intensities in Annular Arrangements of Radioactive Source, Sample, Cylindrical Collimator and Detector

ABSTRACT A Monte Carlo (MC) computer program for the calculation of the distribution of characteristic X-ray intensities as a function of the counting geometry is described. The program evaluates the contribution to the intensities of a fluorescent line from each point of the source, sample and detector. The main considerations of the calculation are based on the critical nature of the internal geometry of the main analyzer components within an energy dispersive X-ray fluorescence (EDXRF) spectrometer. The K XRF intensities for the inner and outer radius of the annular-sample and collimator radius were measured. An optimum geometry can be obtained by varying the collimator radius and the detector-sample distance. The results of the calculations show that the intensity distribution of the radioisotope excited fluorescent radiation through annular sample area is strongly dependent on the collimator radius, with a maximum intensity effect with a smaller sample area and with decreasing collimator radius. An i...

Valence-electron configuration of Ti and Ni in TixNi1−x alloys from Kβ-to-Kα X-ray intensity ratio studies

Kbeta-to-Kalpha X-ray intensity ratios of Ti and Ni have been measured in pure metals and in alloys of Ti(x)Ni(1-x) (x=0.7, 0.6, 0.5, 0.4 and 0.3) following excitation by 22.69 keV X-rays from a 10 mCi (109)Cd radioactive point source. The valence-electron configurations of these metals were determined by corporation of measured Kbeta-to-Kalpha X-ray intensity ratios with the results of multiconfiguration Dirac-Fock calculation for various valence-electron configurations. Valence-electron configurations of 3d-transition metals in alloys indicate significant differences with respect to the pure metals. Our analysis indicates that these differences arise from delocalization and/or charge transfer phenomena in alloys. Namely, the observed change of the valence-electron configurations of metals in alloys can be explained with the transfer of 3d electrons from one element to the other element and/or the rearrangement of electrons between 3d and 4s, 4p states of individual metal atoms.

Measurement of Lι, Lα, Lβ and Lγ X-ray fluorescence cross-sections in Hg, Tl, Pb and Bi for the exciting photons of 16.90– energy

Abstract L i ( i = ι , α , β , γ ) X-ray fluorescence (XRF) cross-sections have been measured for the elements Hg, Tl, Pb and Bi using photon energies of 16.90, 22.58, 25.77, 32.89, 38.18, 43.95, 50.21 and 59.54 keV . L X-rays fluorescence spectra were measured using a Si(Li) detector coupled to a computerized multi-channel analyser in a π /2 experimental geometry set-up. Experimental cross-sections have been compared with the theoretical values of L X-rays cross-sections and fairly good agreement is observed between the experimental and theoretical values.

Effect of external magnetic field on valence-electron structures of Fe and Ni in Invar, Permalloy and the other Fe–Ni alloys by using Kβ-to-Kα X-ray intensity ratios

The effect of external magnetic field on the valence-electron structures of Fe and Ni in various Fe-Ni alloy compositions was investigated by using X-ray fluorescence spectroscopy. Firstly, Kβ-to-Kα X-ray intensity ratios of Fe and Ni in Invar (Fe0.64Ni0.36), Permalloy (Fe0.20Ni0.80) and FexNi1-x (x=0, 0.40, 0.52, 0.55, 0.61, and 1) alloys were measured without any magnetic field and under 0.5 and 1T external magnetic fields, separately. Later, the valence-electron structures of Fe and Ni in both pure form and alloys were obtained by comparison of measured X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations. The results obtained for valence-electron structures of Fe and Ni in various Fe-Ni alloys were evaluated in terms of magnetic field effect, delocalization and/or charge transfer phenomena. The results have shown that valence electron structure of Fe and Ni in Fe-Ni alloys are dependent on both external magnetic field and concentration of alloy elements.

Determination of K shell XRF parameters and K to L shell vacancy transfer probabilities of ferromagnetic 3d transition metals

In this study, K shell X-ray fluorescence cross-sections (σKα, σKβ and σK), K shell fluorescence yields (ωK) and K to L shell vacancy transfer probabilities (ηKL) of ferromagnetic 3d transition metals (Fe, Co, Ni) were investigated to understand how the relationship between ferromagnetism and these values changes with atomic number by using energy dispersive X-ray fluorescence (EDXRF) technique. The all obtained experimental and theoretical results were comparatively given as a function of the atomic number. It was clearly observed that all of the investigated parameters depend on the atomic number and the ferromagnetism state of the atom.

Investigation of alloying effects on XRF parameters of 3d transition metals in Permendur49, Kovar and Ti 50 Co 50 alloys

Abstract The alloying effects on X-ray fluorescence (XRF) parameters such as K shell fluorescence cross-sections (σKα, σKβ and σK), K shell average fluorescence yields (ωK) and K to L shell vacancy transfer probabilities (ηKL) of V, Ti, Fe, Co and Ni 3d transition metals in Permendur49 (Fe49Co49V2), Kovar (Fe54Ni29Co17) and Ti50Co50 alloys have been carried out by X-ray fluorescence studies. K X-ray intensity ratios of these 3d transition metals in both pure form and present alloys have been measured following excitation by 22.69 keV X-rays from a 10 mCi 109Cd radioactive point source. The characteristic K-X-ray spectra from samples were detected by a high-resolution Si(Li) solid-state detector. The investigated fluorescence parameters of present 3d transition elements in alloys indicate significant differences with respect to the pure metals. Consequently, the observed change of the investigated fluorescence parameters can be attributed to the delocalization and charge transfer phenomena between the 3d elements in alloys.

Alloying effect on K shell X-ray fluorescence cross-sections and yields in Ti-Ni based shape memory alloys

Abstract K shell X-ray fluorescence cross-sections (σKα, σKβ and σK), and K shell fluorescence yields (ωK) of Ti, Ni both in pure metals and in different alloy compositions (TixNi1-x; x = 0.3, 0.4, 0.5, 0.6, 0.7) were measured by using energy dispersive X-ray fluorescence (EDXRF) technique. The samples were excited by 22.69 keV X-rays from a 10 mCi Cd-109 radioactive point source and K X rays emitted by samples were counted by a high resolution Si(Li) solid-state detector coupled to a 4 K multichannel analyzer (MCA). The alloying effects on the X-ray fluorescence (XRF) parameters of Ti-Ni shape memory alloys (SMAs) were investigated. It is clearly observed that alloying effect causes to change in K shell XRF parameter values in Ti-Ni based SMAs for different compositions of x. Also, the present investigation makes it possible to perform reliable interpretation of experimental σKα, σKβ and ωK values for Ti and Ni in SMAs and can also provide quantitative information about the changes of K shell X-ray fluorescence cross sections and fluorescence yields of these metals with alloy composition.