2p3/2−13x−1–3x−13d3/2−1 x‐ray satellites in the Lα2 region

The energies and intensities of the various transitions corresponding to the transition scheme 2p_3/2^?13x^?1–3x^?13d_3/2^?1 (i.e. L₃M_x–M_xM₄) were used to compute theoretical Lα₂ satellite spectra in 13 elements in the atomic number range of 62 ≤ Z ≤ 90. The energies were calculated using available HFS data on K–LM and L–MM transition energies. The intensities of all the possible transitions were estimated by considering cross‐sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross‐sections for initial two‐hole states 2p_3/2^?13x^?1 (L₃M_x) amongst various allowed transitions from these initial states to 3x^?13d_3/2^?1 (M_xM₄) final states. Each transition was assumed to give rise to a Gaussian line and the overall spectrum was computed as the sum of these Gaussian curves. The calculated spectra were compared with the available measured Lα satellite spectra. The peaks in the theoretical satellite spectra were identified as the experimentally reported satellites Lα_s, La₁₃, La₁₄ and La₁₇, which lie on the high‐energy side of the Lα₂ dipole line. Copyright © 2005 John Wiley & Sons, Ltd.     

Thickness and angular dependence of the L‐edge X‐ray absorption of nickel thin films

We report on the near‐edge X‐ray absorption fine structure spectroscopy of the L₃ (2p_3/2) and L₂ (2p_1/2) edges for ferromagnetic pure nickel transition metal and show that the L_2,3 edge peak intensity and satellite feature at ~6 eV above the L₃ edge in nickel increase with increasing nickel film thickness both in the total electron yield and transmission modes. The absorption spectra of nickel metal, however, exhibit strong angular‐dependent effects when measured in total electron yield mode. In addition, we calculated the mean electron escape depth of the emitted electrons (λ_e), which was found for pure nickel metal to be λ_e=25 ± 2 Å. We point out the advantages of the total electron yield technique for the study of the L‐edge of 3d transition metals. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Lβ2 satellites in the X‐ray emission spectra of elements 72Hf, 73Ta, 74W, 81Tl, 83Bi and 92U

The satellite spectra arising due to the L₃M_x–M_xN_4,5 (x = 1–5) transition array in the X‐ray emission spectra of ₇₂Hf, ₇₃Ta, ₇₄W, ₈₁Tl, ₈₃Bi and ₉₂U have been calculated using available HFS data on K–LM and L–MN Auger transition energies. The agreement between the calculated and measured energies, that between calculated and measured separations in energies and the consideration of the relative probabilities of all the L₃M_x–M_xN_4,5 transitions have been used as the basis for deciding the origin of the satellites. It has been established that two satellites observed in the Lβ₂ region of the X‐ray spectra of various elements, named β₂^I and β₂^II in the order of increasing energy, are mainly emitted by the L₃M_4,5–M_4,5N_4,5 transitions. It is observed that satellite β₂^I in the spectra of elements with ₇₂Hf to ₇₄W has been assigned to the superposition of the ³F₄–³G₅ and ³F₄–³D₃ transitions and must be the most intense one among all these satellites. The same transition has been proved to be the main origin of satellite β₂^II, reported in the element with ₈₁Tl, ₈₃Bi and ₉₂U. Further, satellite β₂^I, reported in the spectra of elements with ₈₁Tl and ₉₂U, has been associated with the transitions ³D₃–³F₄ and ¹D₂–¹F₃. Finally, line β₂^II, reported in the spectra of elements with Z = 72–74, has been assigned to the ¹F₃–¹G₄ and ³P₀–³D₁ transitions. The possible contributions of other transitions of the L₃M_x–M_xN_4,5 (x = 1–5) array having intensities comparable with those of the above transitions, as well as the corresponding lines that have not yet been observed, have also been discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Improved charge transfer multiplet method to simulate M‐ and L‐edge X‐ray absorption spectra of metal‐centered excited states

Charge transfer multiplet (CTM) theory is a computationally undemanding and highly mature method for simulating the soft X‐ray spectra of first‐row transition metal complexes. However, CTM theory has seldom been applied to the simulation of excited‐state spectra. In this article, the CTM4XAS software package is extended to simulate M_2,3‐ and L_2,3‐edge spectra for the excited states of first‐row transition metals and also interpret CTM eigenfunctions in terms of Russell–Saunders term symbols. These new programs are used to reinterpret the recently reported excited‐state M_2,3‐edge difference spectra of photogenerated ferrocenium cations and to propose alternative assignments for the electronic state of these cations responsible for the spectroscopic features. These new programs were also used to model the L_2,3‐edge spectra of Fe^II compounds during nuclear relaxation following photoinduced spin crossover and to propose spectroscopic signatures for their vibrationally hot states.     

Physical parameters for atomic inner‐shell photoionization processes and analytical applications: a status report

The atomic inner‐shell vacancy decay processes comprising of radiative and non‐radiative transitions are characterized by the physical parameters, namely, the photoionization cross‐sections; X‐ray, Auger and Coster–Kronig (CK) transition rates; fluorescence and CK yields; and the vacancy transfer probabilities. These parameters are required to calculate the K‐shell and L_i (i = 1–3)/M_i (i = 1–5) sub‐shell X‐ray production cross‐sections and relative intensities which, in turn, are needed for different analytical applications. This report intended to provide a detailed account of the currently available data sets of different physical parameters for use in various analytical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimization of L‐shell X‐ray fluorescence detection of lead in bone phantoms using synchrotron radiation

Closely related toxicity and retention mechanisms of lead (Pb) in the human body involve the bone tissues where Pb can accumulate and reside on a time scale ranging from years to tens of years. In vivo measurements of bone Pb can, therefore, play an important role in a comprehensive health risk assessment of Pb exposure. In vivo L‐shell X‐ray fluorescence (LXRF) measurement of bone Pb was first demonstrated over 4 decades ago. Implementation of the method, however, encountered challenges associated with low sensitivity and calibration procedure. In this study, the LXRF measurement was optimized by varying the incident photon energy and the excitation‐detection geometry. The Canadian Light Source synchrotron radiation was used to compare 2 different excitation‐detection geometries of 90^° and 135^° using 3 different X‐ray photon energies: 15.8, 16.6, and 17.5 keV. These energies optimized excitation of the L₃ subshell of Pb and simulated the most intense K‐shell emissions of zirconium, niobium, and molybdenum, respectively. Five rectangular plaster‐of‐Paris bone phantoms with Pb concentrations of 0, 7, 17, 26, and 34 μg/g, and one rectangular 3.1‐mm‐thick resin phantom mimicked the X‐ray attenuation properties of human bone and soft tissue, respectively. Optimal LXRF detection was obtained by the 15.8‐keV energy and the 90^° and 135^° geometries for the bare bone and the bone and soft tissue phantoms, respectively.     

Raman spectroscopy of the transition of α‐gallium oxyhydroxide to β‐gallium oxide nanorods

The thermo‐Raman spectra of synthesised α‐gallium oxyhydroxide nanorod prove that the transition of α‐gallium oxyhydroxide to β‐gallium oxide nanorods occurs above 350 °C but below 400 °C. Scanning electron microscopy proves that the morphology of the α‐gallium oxyhydroxide nanorods is retained upon calcination to β‐gallium oxide. X‐ray diffraction patterns show that the nanorods are α‐gallium oxyhydroxide converting upon calcination to β‐gallium oxide. Intense Raman bands are observed at 190, 262, 275, 430, 520, 605, and 695 cm⁻¹, which undergo a red shift of ∼5 cm⁻¹ upon heating to 350 °C. Upon thermal treatment above 350 °C, the Raman spectrum shows a significantly different pattern. Raman bands are observed at 155, 212, 280, 430, 570, and 685 cm⁻¹. The thermo‐Raman spectra are in harmony with the TG and DTG patterns, which show that the reaction of α‐gallium oxyhydroxide to β‐gallium oxide occurs at 365 °C. Copyright © 2008 John Wiley & Sons, Ltd.     

Thin‐film characterization with x‐ray microanalysis. Extending and improving invariant embedding results

Invariant embedding theoretical results for the recorded x‐ray intensities in electron probe microanalysis were used to develop a procedure for thin films. The method presented here gives the possibility of achieving thin‐film characterization directly from characteristic x‐rays intensities measurements, without the necessity to make an explicit calculation of the ?(ρz) function. Theoretical results are found to follow the general trend of experimental data. Copyright © 2003 John Wiley & Sons, Ltd.     

Chemical effects of high‐resolution YbLγ4 emission spectra: a possible probe for chemical analysis

An ‘eccentric’ X‐ray emission, YbLγ₄, was measured for Yb metal, Yb₂O₃, YbF₃, β‐YbAlB₄, YbNi₃Al₉, and YbNi₃Ga₉ with a resolution of ~0.9 eV. Peak splitting of the YbLγ₄ line was observed in all the recorded spectra and was attributed to the two components originating from the LS coupling of the Yb5p hole, the Yb5p_1/2 (L_IO_II: Lγ₄′) and Yb5p_3/2 components (L_IO_III: Lγ₄). The spectra were substantially different depending on the chemical environment of Yb. The position of the Lγ₄ + Lγ₄′ band shifts depending on the valence of Yb (v): ~4.4 eV from divalent to trivalent. The Lγ₄ + Lγ₄′ spectra of the mixed valence intermetallics, i.e. YbNi₃Ga₉ (v = 2.59) and β‐YbAlB₄ (v = 2.75), were fairly well reproduced by averaging the spectra of divalent Yb and trivalent YbNi₃Al₉, which suggests the possibility of using the YbLγ₄ emission for determining the valence of Yb intermetallics. In trivalent Yb compounds, the relative intensity of Lγ₄ compared with that of Lγ₄′, as well as the appearance of a high‐energy satellite, was found to be influenced by the ligands around the Yb ions. With the aid of preliminary atomic multiplet and band structure calculations, the differences in the valence band structure and resultant screening effects on the O_II,III^?1 states were determined to be the possible causes for the observed ligand dependence. © 2013 The Authors. X‐ray spectrometry published by John Wiley & Sons, Ltd.     

A study of KαL1 X‐ray satellite spectrum of the elements 27 ≤ Z ≤ 31 by photon excitation

K _α X‐ray satellite spectra of Co, Ni, Cu, Zn, and Ga generated by photon excitation are analyzed using a wavelength dispersion spectrometer. Spectra of Ni, Cu, Zn, and Ga are studied for the first time using a LiF420 crystal. Spectrum of Co was studied with LiF200 crystal in second order. K_αL¹ X‐ray satellite energies and relative intensities are measured. The energy shifts relative to diagram line are computed and are compared with theoretical and semi‐empirical values. Dependence of energy shifts and relative intensities on Z and mode of excitation is analyzed.     

Influence of crystal structure,ligand environment and morphology on Co L‐edge XAS spectral characteristics in cobalt compounds

The electronic structure of a material plays an important role in its functionality for different applications which can be probed using synchrotron‐based spectroscopy techniques. Here, various cobalt‐based compounds, differing in crystal structure, ligands surrounding the central metal ion and morphology, have been studied by soft X‐ray absorption spectroscopy (XAS) at the Co L‐edge in order to measure the effect of these parameters on the electronic structure. A careful qualitative analysis of the spectral branching ratio and relative intensities of the L₃ and L₂ peaks provide useful insight into the electronic properties of compounds such as CoO/Co(OH)₂, CoCl₂.6H₂O/CoF₂.4H₂O, CoCl₂/CoF₂, Co₃O₄ (bulk/nano/micro). For further detailed analysis of the XAS spectra, quantitative analysis has been performed by fitting the spectral profile with simulated spectra for a number of cobalt compounds using crystal field atomic multiplet calculations.     

EPMA mapping method for small particles of Al3Fe,Al6Fe, α‐AlFeSi and β‐AlFeSi in 1050‐H18 aluminum sheets

We developed an EPMA mapping method for small Al_aFe_bSi_c particles in 1050‐H18 aluminum sheet, which is one of the base materials coated by photoresist in advance called PS plate (pre‐sensitized printing plate). In this method, we used the ratios of relative x‐ray intensities, I_Fe/I_Al and I_Fe/I_Si instead of the mass ratios, Fe/Al and Fe/Si, of the main elements which constitute the particles and tried to determine the ratios of relative x‐ray intensities using Monte Carlo calculations. Furthermore, using this developed mapping method, we performed the mapping of small Al_aFe_bSi_c particles such as Al₃Fe (0–3%Si as impurities), Al₆Fe (0–1%Si as impurities), α‐AlFeSi(Al_8.3Fe₂Si) and β‐AlFeSi(Al_8.9Fe₂Si₂) in 1050‐H18 aluminum sheets. We found that the discrimination of these particles was achieved with this mapping method. We confirmed that this method is useful for the mapping of Al_aFe_bSi_c particles in 1050‐H18 aluminum sheets. Copyright © 2004 John Wiley & Sons, Ltd.     

Finite lifetime broadening of calculated X‐ray absorption spectra: possible artefacts close to the edge

X‐ray absorption spectra calculated within an effective one‐electron approach have to be broadened to account for the finite lifetime of the core hole. For methods based on Green's function this can be achieved either by adding a small imaginary part to the energy or by convoluting the spectra on the real axis with a Lorentzian. By analyzing the Fe K‐ and L_2,3‐edge spectra it is demonstrated that these procedures lead to identical results only for energies higher than a few core‐level widths above the absorption edge. For energies close to the edge, spurious spectral features may appear if too much weight is put on broadening via the imaginary energy component. Special care should be taken for dichroic spectra at edges which comprise several exchange‐split core levels, such as the L₃‐edge of 3d transition metals.     

Vibrational spectroscopy and crystal structure analysis of two polymorphs of the di‐amino acid peptide cyclo(L‐Glu‐L‐Glu)

Cyclo(L ‐Glu‐L ‐Glu) has been crystallised in two different polymorphic forms. Both polymorphs are monoclinic, but form 1 is in space group P2₁ and form 2 is in space group C2. Raman scattering and FT‐IR spectroscopic studies have been conducted for the N,O‐protonated and deuterated derivatives. Raman spectra of orientated single crystals, solid‐state and aqueous solution samples have also been recorded. The different hydrogen‐bonding patterns for the two polymorphs have the greatest effect on vibrational modes with N H and CO stretching character. DFT (B3‐LYP/cc‐pVDZ) calculations of the isolated cyclo(L ‐Glu‐L ‐Glu) molecule predict that the minimum energy structure, assuming C₂ symmetry, has a boat conformation for the diketopiperazine ring with the two L ‐Glu side chains being folded above the ring. The calculated geometry is in good agreement with the X‐ray crystallographic structures for both polymorphs. Normal coordinate analysis has facilitated the band assignments for the experimental vibrational spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Li‐, Sb‐ and Ta‐modified (K,Na)NbO3 nanopowder prepared via a water‐based sol–gel method

Stable Li‐, Sb‐ and Ta‐modified (K, Na)NbO₃ (LTS‐KNN) sol and gel were successfully prepared via an economical water‐based sol–gel method. Simultaneous thermogravimetry and differential scanning calorimetry (TG‐DSC) and X‐ray diffraction showed that organic compounds were eliminated and a pure perovskite phase formed around 600 °C. Transmission electron microscopy showed that the LTS‐KNN particle size was in the range of 11–34 nm after decomposition at 600 °C. Moreover, high performance LTS‐KNN ceramic was successfully prepared at a low sintering temperature of 1000 °C by use of the nanopowder, and its room‐temperature d₃₃, K_p, K and loss are 311 pC/N, 46.8%, 1545 and 0.024, respectively. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Calibration of the MER α‐particle x‐ray spectrometer for detection of ‘invisible’ OH and H2O possibly present in Martian rocks and soils

An existing Monte Carlo code was modified and extended to predict the intensity ratio of elastically and inelastically scattered plutonium Lα x‐rays incident on rock samples in the Mars Exploration Rover's α‐particle x‐ray spectrometer (APXS) device. The systematics of the scatter ratio as a function of effective sample atomic number are explored. The simulated Rayleigh/Compton ratios (R/C)_sim are compared with measured ratios (R/C)_meas that are obtained by fitting APXS spectra of geochemical reference materials using an x‐ray fluorescence version of GUPIX. The quantity K = (R/C)_meas/(R/C)_sim is then plotted against the mean atomic number of the sample to provide a calibration for known samples. Departures of K values of unknown samples from this calibration may then be attributed to the presence of light, ‘invisible’ elements in the sample. This work is part of an ongoing project aimed at developing methods to quantify bound water in Martian rocks analyzed by the present and the next generation APXS instruments. Copyright © 2006 John Wiley & Sons, Ltd.     

Energies and relative intensities of Kα3 and Kα4 x‐ray satellites of sulfur and sulfides by photon excitation

Energies and relative intensities of the K x‐ray satellites K_α4 and K_α3 of sulfur and two sulfides K₂S and FeS are measured by a wavelength dispersive spectrometer. The energy shifts of these satellites relative to the diagram line are compared with Dirac–Fock theoretical values. The energy shifts and relative intensities are examined for chemical effects. Supplementing the present data to the available data, Z dependence of K_α4/K_α3 intensity ratio is studied in the low Z region. Copyright © 2007 John Wiley & Sons, Ltd.