Measurement of K shell fluorescence cross sections and K shell fluorescence yields for the atomic region 22≤Z≤64 by 59.5 keV photons

A new method has been developed to determine K shell fluorescence cross section and K shell fluorescence yields. This method is based on simultaneous measurement of fluorescence radiation and scattered radiation, thus avoiding problems with measuring the source strength and source-to-detector solid angle. The K shell fluorescence cross section and K shell fluorescence yield for 21 elements in the atomic range 22£Z£64 have been measured by using a Si(Li) detector. The obtained results are compared with the other experimental, theoretical and fit values.     

Measurement of angular dependencies of M X-ray differential cross sections and production cross sections using 5.96 keV photons

The differential cross sections of the emission of M-shell fluorescence X-rays from Tl and Pb have been measured by 5.96 keV photons at seven angles ranging from 50° to 110°. The differential cross section is found to decrease with the increasing emission angle, showing an anisotropic spatial distribution of M-shell fluorescence X-rays. Furthermore, M-shell fluorescence cross sections and the average fluorescence yields were measured for Pt, Au, Hg, Tl, Pb, Bi, Th, and U at an excitation energy of 5.96 keV using a Si(Li) detector. The experimental results of the total M X-ray fluorescence cross sections and M-shell fluorescence yields were compared with the theoretical values.This revised version was published online in November 2005 with corrections to the Cover Date.     

L X-ray production cross sections, average L shell fluorescence yield and intensity ratios in heavy elements

L X-ray fluorescence cross sections, and intensity ratios were measured for elements in the 70￡Z￡92 atomic range at the excitation energy 59.5 keV using a Si(Li) detector. Furthermore, L X-ray fluorescence cross sections and intensity ratios were calculated for elements in the same range. The average L shell fluorescence yields were derived using experimental L X-ray fluorescence cross sections and theoretical photoionization cross sections. The obtained results were compared with other experimental and theoretical values. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measurement of L&agr; and Lß X-ray fluorescence cross sections in Er, Ta, W and Au by 16.896–59.543 keV photons

La and Lb X-ray fluorescence cross sections in Er, Ta, W and Au at excitation energies of 16.896, 22.581, 25.770, 32.890, 38.184, 43.949, 50.214 and 59.5 keV were investigated. Measurements were made using a low energy Si(Li) detector coupled to a model 4096 computerized multi-channel analyser. The experimental results were compared with the theoretically calculated values of L X-rays fluorescence cross sections and other experimental results. Good agreement was observed between experimental and theoretical values.     

Measurement of total and photoelectric cross sections of rare earth elements present in compounds for 123.6 keV and 145.4 keV photons

A new, simple and direct method proposed earlier by us has been employed here to measure the total photoelectric cross section of rare earth elements in the range 58 Z 66 present in compounds at 123.6 keV and 145.4 keV photon energies. The K X-ray fluorescence intensities emitted by these elements, from irradiating their compounds by the photons of above energies, are measured using a NaI (Tl) spectrometer system in a 2π geometrical configuration. The K X-ray fluorescence cross sections of the rare earth elements are determined, from which the total photoelectric cross sections are evaluated. Total mass attenuation coefficients of compounds for the K X-ray and the incident radiations respectively have been measured and these values were compared with the corresponding theoretical values and a good agreement between them is obtained.     

Chemical effects on K and L shell production cross sections and transfer probabilities in Nb compounds

In this study, the chemical effects on σ_Ki (i = α, β), σ_Lα cross sections, K_β/K_α X-ray intensity ratios and vacancy transfer probabilities from K to L (η _KL) for pure Nb and Nb compounds were investigated. The samples were excited by 59.5 keV γ-rays from ²⁴¹Am and 5.96 keV photon energy from a ⁵⁵Fe annular radioactive sources. K and L X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. While it was observed that the chemical bonding had an effect on the σ_Kβ, σ_Lα cross sections and K_β/K_α X-ray intensity ratios for compounds, it was almost negligible for σ_Kα cross section because K_α transitions (2P_3/2,1/2→1S_1/2) occurred in inner shells. It is well known that interactions between central element atom and ligands come into existence in valence state, so outer energy levels are sensitive to the chemical environment. The experimental values of σ_Kα cross section and η _KL are in good agreement with theoretically calculated and other experimental values of pure niobium, but the experimental values of the σ_Kβ, σ_Lα cross sections and K_β/K_α X-ray intensity ratios have differences for some compounds because valence electrons have different bond distances and binding energies in different compounds.     

Laser induced fluorescence in NO2: absolute fluorescence cross sections and quantum yields

Spectrally resolved collision-free absolute fluorescence cross sections have been measured, for NO₂ excited, by the second harmonic of the Nd: YAG laser. The total cross section into the 523.0–650.0 nm range was found to be 2.3 × 10^?20 cm². The measured absorption cross section of 1.46 × 10^?19 cm² implies a quantum yield of 16% over this range.     

Photon-induced M-shell X-ray production cross-sections and fluorescence yields in heavy elements at 5.96 keV

Total M-shell X-ray production cross-sections (MXRP) for selected heavy elements between Yb and U at have been measured at 5.96 keV incident photon energy using a Si(Li) detector. The average M-shell fluorescence yields have been derived, using the experimental total M X-ray production cross-sections and theoretical M-shell photoionization cross-sections. Extracted cross-sections and fluorescence yields have been compared with the literature experimental values, theoretical predictions and semiempirical fits.     

Measurement of Cu K and Ag,In and Sn L X-ray production cross sections by low-energy positron impact

Cu K and Ag, In and Sn L X-ray production cross sections by positron impact have been determined experimentally in the energy range below 30 keV using an X-ray detector with thin Si(Li) crystals. These values have been compared with theoretical estimates derived using the binary encounter formalism. The values for Cu K and Ag L X-rays have also been compared with the results of theoretical calculations using the plane-wave Born approximation with Coulomb and relativistic corrections.     

Chemical effects on L shell fluorescence yields of Ba, La and Ce compounds

Chemical effects on the average L shell fluorescence yields (v_L) for Ba, La and Ce compounds were investigated. Samples were excited by gamma-rays with 59.5 keV energy photons from a ²⁴¹Am radioisotope source. L X-rays emitted by samples were counted by a Si(Li) detector with a resolution 155 eV at 5.9 keV. Chemical effects on the average L shell fluorescence yield (v _L) for Ba, La and Ce compounds were observed. The values are compared with theoretical and experimental ones for the pure elements.     

Simultaneous determination of lanthanides by radioisotope x-ray fluorescence spectrometry based on characteristic K-radiation

The use of radiosiotope-induced x-ray fluorescence is examined for the determination of lanthanides via their characteristic K x-ray lines. Various synthetic mixtures of barium and 14 rare-earth elements were prepared and their homogeneity was checked. The intensity from each mixture was measured for 10 min with excitation by the 88-keV γ-ray from a 3.5-mCi cadmium-109 source or by direct β-particles from a 100-μCi promethium-147 source. Typical spectra and their corrected peak intensities are presented. The spectral backgrounds produced by ¹⁴⁷Pm and ¹⁰⁹Cd are considered.     

Measurement of proton-induced prompt low energy photons by high resolution spectrometry: The analysis of lanthanides

Photons below 200 keV excited by protons from 1.8 to 5.4 MeV were measured from the lanthanides. The K X-rays were sufficiently resolved for analysis, and the sensitivity attainable was or the order of 100 g.g^–1. Apart from La and Ce, all the rare earths also yielded low energy gamma-rays suitable for qualitative analysis and for the determination of minor components at concentrations above mg.g^–1. Some excitation functions are reported and results are given for test analyses of geological materials.     

Total photon attenuation cross sections of helium at energies below 10 keV. An assessment of the accuracy of measured and calculated cross sections

Recent measurements and calculations of helium photoionization, photon attenuation and scattering cross sections for energies below 10 keV are critically evaluated and compared with older measurements, calculations and tabulations. Oscillator strength sum rules are used to assess the validity of various results.     

Large-angle elastic scattering of 59.54keV photons by Kr and Xe

Large-angle elastic scattering of 59.54 keV photons by Kr and Xe is investigated. For Kr, the measured differential cross sections are in good agreement with predictions based on the second-order S-matrix of QED. In case of Xe, the measured cross sections are systematically larger than the predicted ones.     

Analytical formulas for calculation of K X-ray production cross sections by alpha ions

In the present study, different procedures are followed to deduce the semi-empirical and the empirical K X-rayX-ray production cross sections induced by alpha ions from the available experimental data and the theoretical results of the ECPSSR model for elements with 20≤Z≤30. The deduced K X-ray production cross sections are compared with predictions from ECPSSR model and with other earlier works. Generally, the deduced K X-ray production cross sections obtained by fitting the available experimental data for each element separately give the most reliable values than those obtained by a global fit.     

KL 2,3 ionization in neon by electron impact in the range 1.5–50 keV: cross sections and alignment

We have measured the ratio of cross sections σ(KL _2,3)/σ(K) for neon for electron impact in the energy range ofE ₀=1.5 ... 50 keV via the intensity ofKL _2,3?LLL _2,3 Auger satellite lines relative to the intensity ofKL ₁ L _2,3 (³ P) diagram line. The experimental ratio decreases over the full range of energyE ₀ which is contrary to an earlier result by Carlson et al. We have also measured the alignment ofKL _2,3 ¹ P and³ P states via the angular distribution of Auger satellite intensity for the energy rangeE ₀=1.5 ... 4 keV, within experimental error we have found a zero alignment. The totalK Auger spectrum, measured forE ₀=40 keV and at the magic angle of emission ?=54.7°, has been decomposed into its components by using appropriate line shapes distorted by postcollision interaction. Finally, we discussed whether the lines observed at the high-energy side ofKL _2,3?LLL _2,3 Auger satellite lines can be interpreted as structures caused by an angular momentum exchange in the postcollision interaction predicted by Niehaus and Zwakhals.     

Direct determination of total atomic attenuation,total atomic photoelectric and total atomic scattering cross sections of Gd,Tb, Dy and Er at 60 keV

A simple and direct method has been used to obtain fairly accurate total atomic attenuation, total atomic photoelectric and total scattering cross sections by measuring the transmission factor and K X-ray fluorescence spectrum induced by 60 keV -rays for Gd, Tb, Dy and Er by employing a Si(Li) detector system in a 2 geometry set-up. All the parameters are compared with their corresponding theoretical values and a good agreement between them is obtained.