Study of L2,3M4,5M4,5 Auger spectra of Zn and Cu in molecular ZnCl2 and (CuCl)3 vapours

L_2,3M_4,5M_4,5 Auger electron spectra of Zn and Cu have been measured in molecular ZnCl₂ and (CuCl) ₃ vapours. The spectra have been analyzed and compared with the corresponding free-atom spectra. It is found that the main features of the spectra are atomic-like. The energies are shifted by 0.55 eV in ZnCl₂ and by 3.2 eV in (CuCl)₃ towards higher kinetic energy compared with the corresponding free-atom spectra. For the intensity ratios between the L₃ and L₂ groups, the values 2.8 and 3.7 are obtained for Zn and Cu, respectively. These intensity ratio, together with energy considerations based on free-atom Dirac—Fock calculations and observed Auger shifts, indicate that the L₂L₃M_4,5 Coster—Kronig process is energetically possible in (CuCl)₃ molecular clusters but not in ZnCl₂. The satellite structure in the spectra studied also supports this conclusion.     

Mössbauer study of the FeCl3L3 type complex

The measurements of isomer shift and quadrupole splitting of the FeCl₃L₃ (L = ligand) by the Mössbauer effect suggest that the addition of ligand did not change the valence state of the iron ion and has distorted octahedral symmetry.     

Atomic charges in Mg2SiO4 (forsterite), fitted to thermoelastic and structural properties

First and second derivatives of cohesion energy of forsterite with respect to cell edges (generalized Born-Mayer model) are related to thermoelastic tensors; first derivatives with respect to five structural parameters (rotation angle of the SiO₄ tetrahedron, translations of Si and Mg(2) atoms) are set equal to zero by the zero-force principle. All differentiations are performed by keeping constant the internal geometry of the SiO₄ group. Fourteen equations are then obtained and solved numerically in the magnesium and oxygen atomic charges, and in three repulsive parameters, considered as unknowns. The best fitting charge distribution is: z_Mg = 1.38, z_o = ?1.05, z_si = l.44 e. Elastic constants are reproduced with an average relative deviation of 4%, and calculated atomic positions show an average shift of 0.014 A from experimental values. Results are discussed and compared with atomic charges determined from X-ray electron density measurements and vibrational spectroseopy data.     

Sputtering of Ta2O5 by Ar+ ions at energies below 1 keV

The sputtering of anodically formed Ta₂O₅ layers of about 3500 Å thickness has been studied by Sputtered Neutral Mass Spectroscopy (SNMS). For perpendicular bombardment with Ar⁺ ions up to 900 eV the flux of ejected neutral particles is found to consist almost exclusively of metal atoms Ta and Oxide specific molecules TaO and TaO₂ with intensity ratios in the order 1 : 1 : 10^?1. From depth profiling measurements with SNMS, and from the intensity ratios in the SNMS spectra the total sputtering yield of Ta₂O₅ and the partial yields of Ta, TaO and of oxygen have been determined for normally incident Ar⁺ ions of 100 to 600 eV. After an initial increase the TaO intensity in the SNMS spectra remains constant during the sputter removal of the whole layer. A simple model is derived by which the preferred emission of TaO molecules, and the initial increase of the TaO intensity is referred to ion induced variations of the surface stoichiometry of Ta₂O₅. For optimum TaO production the model predicts equal atomic surface concentrations of Ta and O.     

Chemical shift of the Ga and As Kα1,2 and Kβ1,3 X-ray emission lines

By means of a double crystal spectrometer and a computer the chemical shifts of the Ga Kα_1,2, As Kα_1,2 and Kβ_1,3 lines were determined with high accuracy. An interpretation of the results obtained with a free ion model and a calculation according to the Hartree method shows agreement of the values calculated for the effective atomic charges with those based on chemical experience, and also the presence of a charge transfer from the A atom to the B atom in A^IIIB^V compounds. The existence of binding charges is one of the reasons for the fact that |q_A| ≠ |q_B|. The interpretation of the Kβ_1,3 and Lα shifts shows the limitations of the free ion model.     

Sn Mössbauer spectroscopy of Gd0.8L0.2Mn6Sn6 and Tb0.8L0.2Mn6Sn6 compounds (L=Sc,Y, Lu)

The HfFe₆Ge₆-type compounds Gd_0.8L_0.2Mn₆Sn₆ and Tb_0.8L_0.2Mn₆Sn₆ (L = Sc, Y, Lu) have been studied by ¹¹⁹Sn Mössbauer spectroscopy. The values of the apparent quadrupolar splitting clearly evidence the easy plane magnetization of the gadolinium compounds and the easy axis one in the terbium compounds. The three tin sites behave differently with the nature and size of the substituting L element. For a given series, the hyperfine field of the Sn_2d site is almost unchanged whatever the size of the L element. The hyperfine field of the Sn_2e site strongly varies with the L size in relation with atomic displacements. The hyperfine field of the Sn_2c site exhibits a more complicated behavior. The field difference in the easy plane and easy axis compounds confirms the angle-dependent anisotropic contribution of the Mn moment to the hyperfine field. The analysis of the results also suggests the play of angle-dependent contributions arising from the rare earth moment.     

X-ray L1, L2 and L3 absorption limits of 4D transition metals

The wavelengths and energies of the L₁, L₂ and L₃ absorption limits in Zr, Nb, Ru, Rh, Pd and Ag metals have been measured and some of the previous reported values have been found to be incorrect. By comparing the energies of the absorption limits with those of the Lγ₁Ly, and Lβ_2,15, lines and also with the binding energies obtained by XPS, the electronic transitions corresponding to the respective absorption limits have been clarified. It is concluded that (i) the end level of the electronic transition corresponding to the L₁ absorption limit of Zr-Ag is the 5p-like level, and (ii) the end level corresponding to either of the L₂ and L₃, absorption limits of Zr-Pd is the 4d level, while that of Ag is, rather unexpectedly, the top of the 5s level.     

The S1−S0 transitions of 1,2,3-trimethylbenzene and 3-fluoro-1,2-dimethylbenzene observed by two-photon spectroscopy

Two-photon (TP)-induced transitions to the ¹L_b state of 1,2,3-trimethylbenzene and 3-fluoro-1,2-dimethylbenzene were studied by resonant multiphoton ionization in a supersonic jet beam. In both molecules the TP S₁ ← S₀ transition has very strong Franck-Condon components and components vibronically induced by ν₁₄. Seven fundamental vibrations of the ¹L_b state are detected in each molecule. A band, which appears near 14₀¹ due to a Fermi resonance, is proposed to be 1₀²15₀¹. The ¹L_b intensity of the heterosubstituted compound is in agreement with the TP orientation intensity rules.     

Theory of spin-polarized Auger electron spectra in ferromagnetic materials with particular attention to L23M23M23 Auger spectrum in Fe83B17

Spin polarization of L₂₃M₂₃M₂₃ Auger electrons from ferromagnetic Fe₈₃B₁₇ is calculated with a simplified model, and compared with recent experiments. The Auger electron spectrum has two peaks, corresponding to the singlet and triplet final states of a 3p hole pair. It is shown that the spin polarizations of the singlet and triplet peaks, respectively, originate from the exchange interaction between 3d and 2p spins and that between 3d and 3p spins. Similar effects are expected to be observed commonly for L₂₃M₂₃M₂₃ Auger electrons from various ferromagnetic materials including transition elements.     

The local environment of cations in Bi12.5Er1.5ReO24.5

The local environments of cations in a recently reported δ-Bi₂O₃-related phase stabilised by erbium and rhenium, and which shows exceptionally high oxide ion conductivity at low temperatures, have been examined by Bi L_III-, Er L_III- and Re L_III- edge extended X-ray absorption fine structure (EXAFS) measurements. The Bi L_III- and Er L_III- edge data recorded from the compound Bi_12.5Er_1.5ReO_24.5 revealed a high level of oxygen disorder and the adoption by bismuth and erbium of different local environments than those previously observed in erbium-doped δ-Bi₂O₃. The Re L_III edge EXAFS recorded from Bi_12.5Er_1.5ReO_24.5 endorsed the highly disordered nature of the oxygen system and showed rhenium to adopt fourfold oxygen coordination and to be significantly different from that of the local environment of rhenium in Bi₂₈Re₂O₄₉.     

Surface oxidation study of Fe67Co18B14Si1 metallic glass using Auger electron spectroscopy

Surface composition and depth profile of native oxide on Fe₆₇Co₁₈B₁₄Si₁ metallic glass has been investigated using Auger electron spectroscopy. The native oxide is compared with chemisorbed oxygen on the cleaned surface. Results indicate that boron segregates on the surface in the presence of oxygen. The low energy L₂₃M₄₅M₄₅ peak of iron in metallic glass is compared with that in crystallized sample and pure iron foil.     

On the intensity ratio I(KL2,3L2,3)/I(KL1L1) of the auger carbon lines in series of d-metal carbides

C KVV Auger spectra have been obtained for series of nd-metal carbides (n = 3,4 and 5). The numbers of electrons participating in the C KVV Auger processes for these compounds are estimated by considering the intensity ratio I(KL_2,3L_2,3)/I(KL₁L₁). It is concluded that to explain the high intensities of the KL_2,3L_2,3 Auger lines for the d-metal carbides, it is necessary to consider the participation of conduction-band electrons (and/or interatomic transitions) in the C KVV Auger decay process.     

Intensity measurements for the (2, 0) γ-band of O2, b1Σ+g−X3Σ-g

Quantitative intensity measurements have been made for the oxygen γ-band at 6280 Å. Intensities for 19 individual rotational lines of the P_P and P_Q branches and the intensity of the combined R_R and R_Q branches are reported. The band intensity, S^v′_v^″, is found to be 1.52±0.07 cm^-1km^-1atm^-1 (STP).     

Solid-state shifts in the L3M4,5M4,5 Auger spectra of the elements Cu TO Se

The kinetic-energy shifts between atomic and solid-state L₃M_4,5M_4,5 Auger electron spectra of Cu, Zn, Ga, Ge, As, and Se are determined with the aid of semiempirically calculated atomic and experimental solid-state Auger energies. The shift values are calculated by applying the thermochemical model to the Auger process. Good agreement is found between the calculated and experimental values.     

A theoretical study of photoelectron spectra of NbO2, MoO2 and RuO2 by cluster models

DV-Xα calculations have been applied to various small clusters of rutile-family dioxides (NbO₂, MoO₂ RuO₂). It appears that by taking into consideration the potential due to the atomic charges, the density, the ionization cross sections of the energy levels, and by summing the density of states (DOS) of the two different clusters representing surface structures, computations on even small clusters provide information which compares well with the experimental XPS spectra.     

Combustion properties of H2/N2/O2/steam mixtures

The present work reports new experimental and numerical results of the combustion properties of hydrogen based mixtures diluted by nitrogen and steam. Spherical expanding flames have been studied in a spherical bomb over a large domain of equivalence ratios, initial temperatures and dilutions at an initial pressure of 100 kPa (T_ini = 296, 363, 413 K; N₂/O₂ = 3.76, 5.67, 9; %Steam = 0, 20, 30). From these experiments, the laminar flame speed $S_L^0$, the Markstein length L’, the activation energy Ea and the Zel'dovich β number have been determined. These parameters were also simulated using COSILAB^® in order to verify the validity of the Mével et al. [1] detailed kinetic mechanism. Other parameters as the laminar flame thickness δ and the effective Lewis number Le_eff were also simulated. These new results aim at providing an extended database that will be very useful in the hydrogen combustion hazard assessment for nuclear reactor power plant new design.     

Electronic excitations in phosphorus-containing molecules. I. Inner shell electron energy loss spectra of PH3, P(CH3)3, PF3 and PCL3

Electron energy loss Spectroscopy has been used to obtain the inner shell electronic excitation spectra of PH₃, PF₃, PCl₃ and P(CH₃)₃ in the phosphorus L-shell (P 2p, 2s) region as well as the respective ligand K -shells (F 1s, C 1s) and L-shell (Cl 2p and 2s) regions. The spectra were obtained under small momentum transfer conditions so that dipole-allowed transitions dominate. An impact energy of 2.5 ke V was used and inelastically scattered electrons were detected at a typical scattering angle of about 1°. A dipoleforbidden transition of unusual character is observed at 135.11 eV in the P 2p spectrum of PCl₃. Although optically forbidden, as indicated by its absence in a soft X-ray absorption spectrum, the intensity of this transition rises very rapidly with increase in momentum transfer.     

Many-electron effect in the angle resolved L3-M23M23 Auger-photoelectron coincidence spectroscopy (APECS) spectrum of metallic Zn

The many-body effect in the L₃-M₂₃M₂₃ Auger-electron spectroscopy (AES) spectrum of metallic Zn is discussed. The lifetime width and residual relaxation energy shift of the two M₂₃-hole state are governed by the (super) Coster-Kronig (sCK) transitions of two M₂₃-hole state. The residual relaxation energy shift and decay width of the two M₂₃-hole state are calculated in an average configuration by an ab initio atomic many-body theory. The agreement with experiment is good. To elucidate the many-body effect in the two-hole states, it is necessary to be able to discriminate individual components of the multiplet-split AES spectrum. We discuss how to discriminate individual components of the multiplet-split L₃-M₂₃M₂₃ AES spectrum of metallic Zn by angle-resolved Auger-photoelectron coincidence spectroscopy (AR-APECS) in order to determine accurately their line shapes, multiplet splitting energies, and spin states (singlet etc.).     

1S0 and 3S13D1 nucleon-nucleon potentials in the quark compound bag model

For nucleons interacting via formation of the quark compound bag the resulting potential is written in a general form. Explicit examples of potentials are constructed in the ¹S₀, ³S₁ and ³S₁-³D₁ states fitted to the experimental data at T_L ? 1 GeV. As an outcome the QCB energy levels (dibaryons) and NN admixture in QCB are obtained in good agreement with theoretical predictions.     

Atomic orbitals and photoelectron intensity angular distribution patterns of MoS2 valence band

The ratio of atomic orbitals contributing to the valence band can be determined from the photoelectron intensity angular distribution (PIAD) by using linearly polarized light and display-type spherical mirror analyzer. The experiment was done for MoS₂ using a linearly polarized light at the photon energy of 45 eV perpendicularly incident to the sample surface. Atomic orbitals contributing to the bands near the Fermi level were investigated. The PIAD patterns around the Γ point showed splitting of intensity. The intensity at the top and bottom K points was strong, while the intensity was weak at the left and right side K points. The PIAD patterns from various kinds of atomic orbitals were calculated. By comparing the experimental PIAD patterns to the simulated ones, we concluded that at the Γ point Mo 4d_z2 and S 3p_z atomic orbitals are the main components and at the K points the Mo 4d_xy atomic orbital is dominant. The atomic orbital Mo 4d_x2−y2 also gives contribution to the PIAD pattern. These results were in good agreement with the coefficients of the atomic orbitals derived using ab initio band calculation.