Relativistic configuration interaction calculations on Kα X-ray satellites of magnesium ions

In this work, the multi-configuration Dirac-Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used to calculate the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα X-ray from Mg III to Mg XI. We also take the contributions from the Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels, into account. The present values for Mg X and Mg XI were in good agreement with the previous experimental and theoretical results. The new data in this work provide reference values for the level lifetimes, charge state distributions, and average charge of magnesium plasmas.     

Kβ X-ray emission from He-like ions

Relativistic calculations on the energies and electric dipole rates of K_β X-rays from 1s3p(¹P₁,³P₁)-1s² (¹S₀) transitions for He-like ions in the range Z=14–54 are carried out using multi-configuration Dirac–Fock (MCDF) wave functions in the active space interaction approach. The contributions from Breit interaction and quantum electrodynamics have also been included in the calculation. An attempt has been made to find a scaling expression for Breit energy in terms of Zα .The scaled Breit energies are in good agreement with the earlier accurate relativistic results and this ensures the reliability of our scaling procedure. The behavior of MCDF wavefunctions for a given J in the non-relativistic limit has also been studied. The calculated K_β X-ray energies and rates agree well with other available experimental and theoretical values.     

Relation between 2p X-ray photoelectron and Kα X-ray emission spectra of manganese and iron oxides

The high resolution Mn and Fe Kα X-ray emission spectra (XES), and Mn and Fe 2p X-ray photoelectron spectra (XPS) for manganese and iron oxides were measured. The spectra were compared with those of [MnO₄]⁻, [Fe(CN)₆]⁴⁻ and [Fe(CN)₆]³⁻ ions. As the electronic structure of the latter compounds do not change with electron hole creation in the core levels, satellite peaks due to charge transfer are not observed in the 2p XPS spectra, and the peak profiles of metal 2p XPS and Kα XES are governed by the exchange splitting between 2p and valence electrons. The metal 2p XPS spectra of the oxides had satellite peaks, but the XES spectra had no satellites. FWHMs of the metal 2p_3/2 main peaks of the compounds being low spin states are smaller than those of metal Kα₁ XES spectra. However, FWHMs of Mn 2p_3/2 of the manganese oxide were nearly equal to those of Mn Kα₁ XES spectra, and those of Fe 2p_3/2 XPS spectra of the iron oxides are greater than those of Fe Kα₁ XES spectra.     

X-ray Lα emission and LIII absorption spectra of copper compounds

The X-ray Lα _{1, 2} emission spectra and L_III absorption spectra in Cu, Cu₂O, CuCl, Cu₂S, CuO, CuCl₂, CuS, CuF₂ and Cu(en)₂Cl₂ are investigated. It is shown that the emission spectra of divalent copper compounds are considerably distorted due to a sharp absorption peak near the L_III edge. The nature of this peak is discussed and a relation is made with satellite peaks in X-ray photoelectron spectra.     

Relativistic configuration interaction calculations for the K α X-ray transitions of Co XV to Co XXVI ions

Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics (QED) and finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock wave functions on the wavelengths, electric dipole rates, oscillator strengths and line strengths of cobalt ions with a single vacancy in the K shell. The calculated values are compared with the other available data on He-like to Be-like cobalt and are found to be in very good agreement with them. This confirms the present calculations. We predict new data for several levels where no other theoretical and/or experimental results are available. These data provide reference values for level lifetimes, charge state distribution and the average charge of cobalt plasmas.     

X-ray emission via Kα resonance complexes in gold ions

The excitation energies from ground state for 63 fine structure levels of the terms belonging to 1 s², 1snl, 2lnl′ (n = 2,3), 3l3l′ (l ≠ ≠ l′) configurations of Au⁷⁷⁺, as well as oscillator strengths for electric-dipole-allowed and intercombination transitions among the fine-structure levels were theoretically evaluated. The important relativistic effects in intermediate coupling are incorporated by means of the Breit–Pauli Hamiltonian. Extensive comparisons are performed with several approximations and previous data sets in order to size up contributing effects and to estimate accuracy ratings. The atomic excitation is obtained by electron impact in close coupling approach. For optically allowed transitions, the electron-impact collision strengths at collision energy up to 80 keV are reported. The results are relevant to the laboratory and astrophysical plasmas.     

Kα X-ray satellite spectra of Ti, V, Cr and Mn induced by photons

K X-ray emission spectra of Ti, V, Cr and Mn generated by photon excitation have been studied with a crystal spectrometer. The measured energy shifts of K_α satellite relative to the diagram line are compared with values obtained by electron excitation and with different theoretical estimates. The present experimental values of K_αL¹/K_αL⁰ relative intensities are compared with values obtained by electron excitation.      

Properties of the Kα X-ray transitions in highly ionized cobalt

Multi-Configuration Dirac–Fock and relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and finite nuclear mass corrections have been carried out in the extended optimal level (EOL) scheme on the transition wavelengths, transition probabilities, absorption oscillator strengths and line strengths of the Kα X-ray from Co XIIX to Co XXVI. The calculated values are compared with the other available data on He-like to Be-like cobalt and are found to be in very good agreement with them. This confirms the present calculations. These data provide reference values for level lifetimes, charge state distribution and average charge of cobalt plasmas.     

XAFS spectra from X-ray fluorescence Kβ line using conventional energy-discriminating detector

X-ray fluorescence spectra of copper (Cu) metal, copper monoxide (CuO), and potassium chromate (K₂CrO₄) were recorded as a function of incident X-ray energy near the Cu K-edge and chromium (Cr) K-edge, respectively, using a conventional silicon drift detector. The spectra contained components due to elastic, inelastic, and multiple scattering, in addition to the Kα and Kβ lines. Cu and Cr K-edge X-ray absorption fine structure (XAFS) spectra of Cu, CuO, and K₂CrO₄ were obtained by an intensity analysis of the Kα and Kβ lines. The intensity of the Kβ line for the different incident photon energies was obtained by numerically removing the additional scattering components using the MUSCAT program. These spectra exhibited a jump near the K absorption edges, which reproduced the spectral features obtained in transmission mode for both Cu, CuO, and K₂CrO₄. A chemical shift was also clearly identified in the X-ray absorption near edges structure using the X-ray fluorescence Kβ line. In addition, the Cr K-edge extended XAFS spectrum of K₂CrO₄ was clearly observed using the Cr Kβ fluorescent line. The XAFS measurements on the Kα and Kβ lines are possible, and they carry equally valuable information.     

Wavelengths,transition probabilities,line strengths and oscillator strengths for the Kα and Kβ X-ray transitions in NiXIX through NiXXVII

Relativistic configuration interaction calculations with the inclusion of Breit interaction, quantum electrodynamics and finite nuclear mass corrections have been carried out in the extended optimal level scheme using multi-configuration Dirac-Fock wavefunctions on the wavelengths, electric dipole transition rates, line strengths and oscillator strengths of nickel. Through the use of the active space method, the calculated values are compared with the other available data on He-like and Be-like nickel and are found to be in very good agreement with them. In this paper we give accurate transition properties from NiXIX through NiXXVII. These data provide reference value for level lifetime, charge state distribution and average charge of nickel plasma. Appendix A and B are only available in electronic form at www.epj.org     

Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters

Absorption spectra for Sn clusters （n=2...8） are calculated using an adiabatic time-dependent density functional formalism within the local density approximation （LDA）. We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA （TDLDA） spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the ＇hard sphere＇ model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.     

X-ray excited auger spectroscopy: selecting the optimum sharpest auger peaks excited by Al Kα, Ag Lα and Ti Kα X-ray radiations

XAS is developing, but, because it suffers from the fact that the “standard” Mg/Al dual anode X-ray gun usually limits the generation of intense Auger peaks to about half of the elements, this is a relatively slow development. It is necessary to obtain the optimum sharpest Auger peaks for high resolution XAS and for the precise determination of Auger Parameters. Therefore, a suitable unmonochromatic X-ray source should be selected for different elements or different transitions of an element. The Quadranode X-ray gun with the ability to emit three ranges (lower, medium and higher) of energy of X-ray photons is an appropriate candidate for modern XAS and XPS applications.     

Reconstruction of all-electron orbitals from one-electron pseudowave functions and calculations of the intensities of Si X-ray emission spectra of Si, β-SiC,stishovite, and β-cristobalite crystals

The intensities of Si X-ray emission spectra of Si, β-SiC, stishovite, and β-cristobalite crystals are calculated. The wave functions of the initial and final states are obtained in the framework of the density-functional theory with the use of the norm-conserving and ultrasoft pseudopotentials. The all-electron crystal orbitals are reconstructed from the one-electron pseudowave functions. The probabilities of X-ray emission transitions are calculated by reconstructing the all-electron orbitals in two different gauges, namely, the length and velocity gauges. The calculated intensities are compared with the experimental spectra and the partial densities of states.     

The use of the Gáspár potential in theoretical investigations of the spectra of atoms and ions

The method of the use of theGáspár potential in theoretical investigations of the energy spectra of atoms and ions in the Hartree—Fock—Pauli approximation is described. The calculations of the energy spectra of a number of multiple-charged ions in the configurations 1s ²2s ²2p ²3s and 1s ²2s ²2p ²3d are presented as the examples and compared with the experimental data available.

     

Evaluation of the Mn Lα and Lβ Spectra of Mn Metal and of Various Mn-Oxides

The Mn Lα and Lβ spectra of Mn, MnO, Mn₃O₄, Mn₂O₃, and MnO₂ have been measured. Each Mn La spectrum has been deconvoluted into two bands, Lα_A and Lα_B, and the integrated Lα_A/Lα_B intensity ratio was found to be inversely proportional to the Mn-0 inter-atomic distance, but proportional to the oxidation number. This finding tends to indicate the likelihood of crossover transition from oxygen to manganese. The intensity ratio Lβ/Lα_B of the pure metal was found to coincide closely with the statistically predicted value of 0.5. Furthermore, for Mn-metal, as well as for the oxides, the shift of the Lα_A band from the Lα_B band was found to agree with the change in the Lβ/Lα peak intensity ratio as a function of oxidation number.     

π-SCF and INDO calculations and the absorption,polarized excitation and circular dichroism spectra of [4]-helicenes

The absorption and circular dichroism spectra of (-)d-1,12-dimethyl-benzo[c]phenanthrene-5-acetic acid are reported, together with the polarized excitation and fluorescence spectra of the parent hydrocarbon, [4]-helicene. The transition energies of 1,12-dimethyl-[4]-helicene calculated in the π-SCF approximation, and the corresponding dipole and rotational strengths obtained by the dipole-velocity method, show that the optical isomer studied has the M-configuration with the stereochemical form of a segment of a left-handed helix. Analogous calculations in the INDO approximation using both the dipole-velocity and the dipole-length procedure with separate consideration of the one-centre and the two-centre transition moment integrals, indicate that the more satisfactory dipole and rotational strengths are obtained in the two-centre dipole-velocity formulation. The appearance of σ → π* transitions at higher energies limits the application of the π-SCF procedure, but the INDO method is found to place these transitions at too low an energy.     

Application of Kβ/Kα in selecting calibration standards for X-ray fluorescence analysis

A method for improving the accuracy in X-ray fluorescence spectroscopy analysis with pressed pellets was established through matching the calibration standards by the Kβ/Kα ratios. The Kβ/Kα ratios of four major elements (Al, Si, Ca, and Fe) were measured in 14 certified reference materials (CRMs) for geochemistry. The deviation of the biggest Kβ/Kα values relative to the smallest ones for the same element was from 1.52% (Si) to 20.98% (Al) when pressed pellets were used. The relative deviation of Kβ/Kα values for Ca was as high as 3.56% even for two soil CRMs (GBW07404 and GBW07408). X-ray diffraction analysis confirmed that the Ca elements in the two CRMs were in distinct phases, thereby leading to the different Kβ/Kα values. The Fundamental Parameter Method (FPM) results of two calibration strategies were compared. When one of the 14 CRMs was selected as unknown sample whereas the other 13 CRMs were used for calibration to determine Al₂O₃, SiO₂, CaO, and Fe₂O₃, the relative errors were 10.80%, 8.77%, 8.33%, and 10.91%, respectively. Another strategy, where only one CRM was used for calibration of samples with large errors, was adopted by matching Kβ/Kα values. The results of calibrating using CRM with similar Kβ/Kα values were more accurate than those with different Kβ/Kα values.     

Diagram,valence-to-core,and hypersatellite Kβ X-ray transitions in metallic chromium

We report on measurements of the Kβ diagram, valence-to-core (VtC), and hypersatellite X-ray spectra induced in metallic Cr by photon single and double K-shell ionization. The experiment was carried out at the Stanford Synchrotron Radiation Lightsource using the seven-crystal Johann-type hard X-ray spectrometer of the beamline 6-2. For the Kβ diagram and VtC transitions, the present study confirms the line shape features observed in previous works, whereas the K^hβ hypersatellite transition was found to exhibit a complex spectral line shape and a characteristic low-energy shoulder. The energy shift of the hypersatellite relative to the parent diagram line was deduced from the measurements and compared with the result of extensive multiconfiguration Dirac–Fock (MCDF) calculations. A very good agreement between experiment and theory was found. The MCDF calculations were also used to compute the theoretical line shape of the hypersatellite. A satisfactory agreement was obtained between the overall shapes of the experimental and theoretical spectra, but deviations were observed on the low- and high-energy flanks of the hypersatellite line. The discrepancies were explained by chemical effects, which were not considered in the MCDF calculations performed for isolated atoms.     

Analysis of the Zeeman effect on D_α spectra on the EAST tokamak

Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis(OSMA) system in EAST tokamak.The Zeeman splitting of the D_α spectral lines has been observed.A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and ±σ components of the D_α atomic spectra to acquire the information of the local plasma.The spectral line shape was investigated according to emission spectra from different regions(e.g.,low-field side and high-field side) along the viewing chords.Each polarization component was fitted and classified into three energy categories(the cold,warm,and hot components) based on different atomic production processes,in consistent with the transition energy distribution by calculating the gradient of the D_α spectral profile.The emission position,magnetic field intensity,and flow velocity of a deuterium atom were also discussed in the context.     

Effects of ambient pressure on Cu Kα X-ray radiation with millijoule and high-repetition-rate femtosecond laser

Hard Cu Kα X-ray radiation was generated with a millijoule and high-repetition-rate Ti: sapphire laser in air, helium or vacuum (2.7–1.3×10⁴ Pa) ambient. The characteristic X-ray was obtained by focusing the 0.06–1.46 mJ/pulse, 100 fs, 1 kHz repetition femtosecond laser onto a solid copper target to a spot 4.8 μm in diameter. The relationship between Kα X-ray conversion efficiency and atmospheric conditions was explained with a simple electron collision model that suggested that the electron mean free path is an important parameter in the generation of ultrafast pulsed X-rays in any ambient condition. We also demonstrated a high-intensity X-ray source working in helium at atmospheric pressure.