K-shell X-ray production for fluorine ions on target elements Ti to La

The production of target atomK-shell X-rays has been studied for 2 to 28 MeV fluorine ions incident on thin solid targets of 14 elements with atomic numbers Z₂=22 to 57. Total X-ray production cross sections, energy shifts ofK _α andK _β lines andK _α/K _β intensity ratios were measured with a Si(Li) detector. The results of cross section measurements are compared with theoretical predictions of inner shell ionization. In most cases, satisfactory agreement between measured cross sections and theoretical Coulomb ionization cross sections, corrected for the perturbation of the target atom by the projectile charge and for relativistic effects, was obtained.     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK _α- andK _β-lines and theK _α/K _β-intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

Inner-shell ionization by relativistic electron impact

K-, L andM-shell ionization cross sections have been measured for 23 elements, 12≦Z≦92, after bombardment with relativistic electrons, 15≦E ₀65MeV, by means of high resolution semiconductor detectors and a recently developed gas-scintillation proportional counter. For constant electron bombarding energyE ₀ the ionization cross sections follow a power law dependence,σ∽Z ^?α, and forE ₀=50MeV we deducedα =2.45±0.02 for theK shell andα=3.00 ±0.09 for theL shell. The observedZ dependence exhibits significant systematic deviations from theoretical predictions which exceed the experimental values up to 15 % at lowZ elements for theK shell and on the average about 11% for theL andM shell. The same behaviour of too low experimental values, i.e. an overestimation by the theory, is observed for the energy dependence of the cross sections for all shells. A scaling behaviour describing theZ andE ₀ dependence for allK-, L andM-shell data points is observed which also predicts the experimental values by other groups at lower and higher energies correctly. The comparsion of the measuredLΒ/Lα, andLγ/Lα intensity ratios for highZ elements with the values obtained by other groups in the energy range 0.3≦E₀≦1,000 MeV exhibits an increase with bombarding energy that cannot merely be explained by the energy dependence of the subshellionization cross sections for theL shell. An attempt to explain this effect with the change of the Coster-Kronig transition probability is described.     

Total attenuation cross-sections of fluorescent X-rays of Zr,Sn, Ba,Au, Pb,Th and U in elements 6⩽Z⩽82

The total attenuation cross-sections in elements 6?Z?82 forK _α andK _β groups of lines of elements Zr, Sn and Ba andL _l ,L _α,L _β andL _γ groups of lines of the elements Au, Pb, Th and U have been measured. The experimentally measured attenuation cross-sections have been found in good agreement with the theoretical estimates.     

The investigation of K‐shell fluorescence parameters of Zn–Fe alloys with different grain size and microstrain values

It is known that zinc alloys with iron group metals have better corrosion resistance than pure zinc. Owing to the corrosion resistance of these alloys, Zn–Fe coatings are widely used in automotive industry and have excellent mechanical performance. In this work, we investigated the relationship between the changes in the measured X‐ray fluorescence parameters (K_β/K_α, σ_Kα and σ_Kβ) and the changes in the structural parameters such as microstrain or grain size values for Zn–Fe alloys that were prepared with different pH values. To explain these changes, the K_α and K_βX‐ray production cross sections, and the K_β/K_αX‐ray intensity ratio values were calculated by three different ways for the elemental forms of Zn and Fe. The structural parameters, such as microstrain and grain size, were also calculated. We expect that the outer shell electronic distribution affects the structural parameters of the produced Zn–Fe alloys, changing the measured K_α and K_βX‐ray production cross sections, and the K_β/K_αX‐ray intensity ratio values. We also show that Zn–Fe alloy mi nimum microstrain value corresponds to the maximum changes in K_βX‐ray production cross‐section values of Fe and Zn. Copyright © 2017 John Wiley & Sons, Ltd.     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

Comparison of inner shell ionization by 16O and 18O projectiles

K-shell ionization induced by oxygen isotopes has been studied for several elements ranging from sulphur to bromine. Ionization cross sections and K_α/K_β intensity ratios are compared at equal projectile velocities.     

The internal conversion of theN=81 Isotones139m Ce and141m Nd

A rapid gas-jet system was used for preparation ofβ ^?-samples of^139m Ce and^141m Nd. Conversion electrons and photons were detected simultaneously with absolutely calibrated detectors. Conversion coefficientsα _K = 0.0732±0.0023 andα _K=0.0824±0.0029, conversion ratiosK/L+...= 4.68±0.20 andK/L+...=4.58±0.23 were measured for^139m Ce, and^141m Nd, respectively. The calculated M4 values of Hager and Seltzer, and Dragoun et al. were confirmed within the experimental accuracy.     

X-ray production by 1.5–11 MeV protons

K-shell ionization andL x-ray production cross-sections by proton impact have been determined from measurements ofK x-ray yields from thin targets of Ti, Fe, Co, Cu, Ni and Ag and ofL x-ray yields from Au and Pb. The proton energies varied from 1.5 to 11 MeV. A Si(Li) semiconductor detector recorded the x-rays. The total error in the measured cross-sections is mostly less than 5%.K _β /K _α ratios andL _l,β,γ /L _α ratios have been determined. Ionization cross-sections have been compared with predictions of the plane-wave Born approximation (PWBA) and the binary-encounter approximation (BEA). Both theories describe the ionization quite well: PWBA is, however, better for higher proton energies whereas BEA is superior for lower energies. An empirical formula for ionization cross-sections is derived.     

On the intensities ofK X rays following thermal neutron capture

Through the measurement of the absolute intensities of theK _α andK _β X rays following slow neutron capture in¹⁵⁵Gd,¹⁷⁶Lu and¹⁹⁹Hg and their comparison with the intensities of theK-conversion electron transitions from the same reaction it is shown that theK X rays are caused only by internal conversion.     

Scattering of <Emphasis Type="Italic">α</Emphasis> particles on <Superscript>11</Superscript>B nuclei at energies 40 and 50 MeV

The differential cross sections for elastic and inelastic scattering of α particles on ¹¹B nuclei at energies of 40 and 50 MeV were measured in the entire angular range. The measured angular distributions were analyzed in terms of the optical model, the distorted-wave Born approximation, and the coupled-channel-method. Optical model potentials and quadrupole (β₂) and hexadecapole (β₄) deformation parameters were found from this analysis. The rise in the cross sections at backward angles was shown to be associated with the transfer mechanism of the heavy ⁷Li cluster.     

Account of the fine structure of hydrogen atom levels in the effective emission cross sections of Balmer lines excited by electron impact in gases and plasma

The possibility of a correct account of the fine structure was shown for two limiting cases observed in beam and plasma experiments. A significant difference was found in the emission cross sections and the rate coefficients of direct and dissociative excitation of the H _α and H _β lines by electron impact in two limiting cases (e.g., this difference reaches an order of magnitude for dissociative excitation of the H _β line). The most reliable data on the cross sections and the rate coefficients of direct and dissociative excitation of the H _α and H _β lines by electron impact were found for both limiting cases. It was shown that, among the first four lines of Balmer series (rather easily detected), only the first two lines, i.e., H _α and H _β, can be currently employed in plasma spectroscopy studies because of the absence of data on the partial excitation cross sections of hydrogen atom nl-sublevels with n≥5.     

HighP ∧ hadron production off nuclei at 70 GeV

Invariant cross sections for hadron production (π^±,K ^± ,p and \(\bar p\) ) by protons off C, Al, Cu, Sn and Pb nuclei have been measured at 70 GeV for theP _∧ range from 1 up to 4.65 GeV/c. TheA-dependence of the invariant cross section is not described by the exponentialA ^α(P _∧), which points to the presence of secondary hadron absorption in nuclei.     

Production of vector and tensor mesons in proton-proton collisions at\sqrt s = 52.5 GeV

Inclusive production of ?⁰,f, andg ⁰ mesons and ofK _s ⁰ ,K ^*0 (892), ? andK ^*0(1430)mesons has been measured at <y>～2.6 and <p _T >～1.1 GeV/c in proton-proton interactions at \(\sqrt s = 52.5\) GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp _T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.     

L-subshell ionization cross sections for Au,Pb, and Bi by 60–600 keV electron impact

TheL ₁-,L ₂- andL ₃-subshell ionization cross sections of Au, Pb and Bi by 60–600 keV electron impact have been determined from the measured x-ray production cross sections. The experimental results have been compared with the relativistic PWBA, the Binary Encounter Approximation (BEA) and the Kolbenstvedt Approximation (KA) calculations. These calculations, especially the relativistic PWBA, give good agreement with the experimental data for theL ₃-subshell. For theL ₁- andL ₂-subshells there are some deviations and these can explain the disagreement observed for theL _α/L _χ- andL _γ/L _χ intensity ratios.     

Relative x-ray transition probabilities to theK-shell forZ=81, 92, 94, and 96

Accurate intensity measurements of the majorK x-ray groups have been performed with high resolution Ge(Li) detectors in singles and coincidence arrangements and with a high-purity Ge detector of the intrinsic type. Previously reportedK x-ray intensities forZ=96 are in error due to the presence of a 121.5 keV γ-ray in the decay of²⁴⁹Cf. The present results are as follows: forZ=81,K _α2/K _α1=0.589±0.008, \(K_{\beta _1^\prime } /K_{\alpha ^1 } = 0.344 \pm 0.008, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.102 \pm 0.004\) , andK _β/K _α=0.281±0.006; forZ=92 \(K_{\alpha _2 } /K_{\alpha _1 } = 0.611 \pm 0.008,K_{\beta _1^\prime } /K_{\alpha _1 } = 0.365 \pm 0.008, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.125 \pm 0.004\) , andK _β/K _α=0.300±0.006; forZ=94, \(K_{\alpha _2 } /K_{\alpha _1 } = 0.610 \pm 0.008, K_{\beta _1^\prime } /K_{\alpha _1 } = 0.369 \pm 0.010, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.127 \pm 0.004\) , andK _β/K _α=0.308±0.008; and forZ=96, \(K_{\alpha _2 } /K_{\alpha _1 } = 0.627 \pm 0.008, K_{\beta _1^\prime } /K_{\alpha _1 } = 0.372 \pm 0.009, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.133 \pm 0.005\) , andK _β/K _α=0.310±0.008. The error limits are the 2σ statistical errors to which a systematic error in the detector efficiencies has been added linearly. The present results are compared with recent theoretical calculations.     

26g,mAl production cross sections from the 23Na(α, n)26Al reaction

Cross sections have been determined for the production of ^{26g, m}Al from the ²³Na(α, n) reaction. Total ²⁶Al production cross sections were obtained from measurements of the thick-target neutron yield. ^26mAl cross sections were measured using an activation technique. ^26gAl cross sections were deduced by subtracting the ^26mAl cross sections from the total (α, n) cross sections. The principle of detailed balance has been applied to the low-energy data to obtain cross sections for the astrophysically interesting ^26gAl(n, α₀)²³Na reaction. These results are compared with the results of Hauser-Feshbach calculations.     

The real part of Kp forward scattering with rising total cross sections

Forward dispersion relations have been applied to Kp elastic scattering with the assumption that the total cross sections continue to rise with primary energy ω like log ω and log² ω respectively. The results depend on the way of approach with ω of the two total cross sections. In this connection, we further discuss the consequences of a generalized version of the Pomeranchuk theorem when total cross sections are rising like log^β ω. The ratio α₊ of real and imaginary parts of the forward elastic scattering amplitude for K⁺ p is seen to change sign, and becomes positive at some high energy (e.g. at about 400 GeV in the log² case). If the total cross section difference behaves like 1/ω^b, then α_ will remain positive at all (high) energies. However, if the cross sections approach each other as slowly as allowed by the generalized Pomeranchuk theorem, then also α_ will change sign at some very high energy.     

L x‐ray fluorescence cross‐sections of heavy elements in the atomic region 57 ≤ Z ≤ 71 excited by 17.78 keV photons

L x‐ray fluorescence cross‐sections (σ_Lα, σ_Lβ, and σ_Lγ) were measured with an accuracy of 6% (except for the Lγ x‐ray line around 8%) for La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu at an excitation energy of 17.78 keV. Relative intensities I_Kβ/I_Kα and I_Lγ/I_Lα were also measured for the same elements. The measured cross‐sections were compared with experimental and theoretical values. Measurements of the emitted x‐rays were performed using an Si(Li) detector. Copyright © 2004 John Wiley & Sons, Ltd.