X-ray Emission Data Research Articles

Free-atom core binding energies from x-ray photoelectron spectroscopy I. Zinc and cadmium

Gas phase photoelectron spectra of zinc and cadmium have been obtained with AlKα radiation. The binding energies measured are: Zn2p1/2 (1052.3 eV), Zn2p3/2 (1029.1 eV), Cd3d3/2 (418.8 eV), and Cd3d5/2 (412.0 eV). Combining x-ray emission data on the solid with free atom optical energy results gives binding energies in close agreement with our values. A decrease of 2.8 eV for Zn2p and 3.3 eV for Cd3d was found in going from the free atom to the metal. This difference is discussed in relation to the various calculations of extra atomic relaxation energies in solids.

The photoelectron spectra of some gaseous thallium(I) oxyanion salts

Abstract The HeI photoelectron spectra of the gaseous forms of TlBO 2 , TlNO 3 , Tl 2 SO 4 , and TlReO 4 have been obtained using a cylindrical mirror electron spectrometer equipped with an internally-located, resistance-heated sample oven. The spectral peaks due to Tl 6 s electrons and those due to the oxyanions have been assigned molecular-orbital origins by use of MO calculations, comparisons with X-ray photoelectron and X-ray emission data, electron diffraction experiments, and mass spectrometric information.

Detection of localized moments of the 3d series by electron energy-loss spectra

The transmission spectra of electrons from the 3p→3d transition of Cr, Mn, Fe, Co and Ni have been measured and analyzed to obtain information about the localization of the d states. By combining this data with soft X-ray emission data we obtain the interband exchange splitting for Fe, Co and Ni to be ≈1.7 eV/μ B.

Time-Resolved X-Ray Spectral Studies of Laser-Compressed Targets

We present temporally and spectrally resolved x-ray emission data from a laser-irradiated target. The temporal dependence is interpreted in terms of a laser heating phase, a plateau period in which the glass-shell pusher propagates radially inward, a secondary x-ray burst corresponding to stagnation of the pusher at the target center, and a rapid decay of emission in the post-compression target disassembly period.

Cluster model for lattice distortion effects on electronic structure: VO and VO2

Molecular cluster predictions for electronic energy levels, wave functions, momentum densities, and Compton profiles of VO and V${\mathrm{O}}_{2}$ are examined within the Hartree-Fock-Slater model. V${\mathrm{O}}_{6}$ clusters are treated in ${O}_{h}$ ${D}_{4h}$ and ${D}_{2h}$ symmetry to obtain quantitative relations between distortion parameters and level shifts and splittings. Effects of the crystal environment are taken into account by a potential field. Our results for VO are consistent with the augmented plane-wave band calculation of Mattheiss and x-ray emission data; the V${\mathrm{O}}_{2}$ levels are in good agreement with x-ray photoelectron spectroscopy data. A sizable anisotropy is predicted for the Compton profile of VO and V${\mathrm{O}}_{2}$.

Orbital relaxation in X-ray emission and ESCA transitions of the vanadate ion

The relaxation effects in X-ray emission and ESCA transitions are studied for the VO 4 3− ion. Using the MSX α method and the transition state procedure the calculations of energy levels for a number of transition states corresponding to the VK β5, VL α, OK α emission spectra, as well as ESCA spectra of valence and core levels, have been carried out. It is shown that the orbital relaxation results in shifts of up to 100 eV for the deep core levels of the ion, but has quite small influence on the valence levels. The results of calculations are compared with the experimental X-ray emission and ESCA data. The approach used appears to be a good approximation not only for calculations of relative positions of spectra bands, but the absolute energies of the X-ray emission and ESCA transitions also.

Molecular orbital effects on the Ti LMV auger spectra of TiO and TiO 2

The fine features of the Auger valence band spectra of TiO and TiO 2 have been related to transitions arising from oxygen 2s and titanium 3d, 4s molecular orbitals. The Auger bands investigated include the L III, M 1N 1, L IIIM 1M 4,5, L IIIM 2,3N 1, and L IIIM 2,3, M 4,5 transitions. The N( E) valence band spectra have been unfolded and the resulting components correlated with X-ray emission data and a molecular orbital (MO) model. Differences in spectral shapes are shown to be linked with differences in the density of state of oxygen—titanium molecular orbitals.

Many-body effects in x-ray photoemission from magnesium

X-ray photoemission experiments were performed on samples of magnesium and aluminum prepared with clean surfaces in ultrahigh vacuum. Core-level binding energies were in excellent agreement with x-ray emission data. Asymmetries in core-level peaks were observed and are compared with theory. The Mg $\mathrm{KLL}$ Auger spectrum showed kinetic energies higher than the literature values. Many-body effects, in the form of extra-atomic relaxation, were present in core levels and Auger lines. Both $K{L}_{1}V$ and $K{L}_{2,3}V$ Auger peaks of Mg were observed. Many-body effects were also manifest as rich plasmon satellite structure accompanying every primary peak. The valence-band spectrum was compared with x-ray emission data and with the $K{L}_{2,3}V$ peak. The spectra were interpreted in terms of energy-level diagrams rather than one-electron "levels." It is argued that valence-band spectra obtained by different methods can be compared most directly among states with the same number of core holes. A hierarchical classification of hole states is suggested. The effect of the degree of localization of the hole state on the relaxation energies in metals is discussed and shown to be small. Finally it was observed that in several light metals the energies required to remove a valence-band electron or a unipositive ion core are about equal.

Metal–ligand bonding in some vanadium compounds: a study based on X-ray emission data

K α And KβX-ray emission spectra of V (metal), [V(pd)3](pd = pentane-2,4-dionate), VF3, VO2, V2O5, [VO][SO4], [NH4][VO3], and [NH4][V3O8] are reported. It is argued that peaks of higher energy than Kβ1,3 are due to transitions involving molecular orbitals with Vp character rather than V 3d. The relative intensities and emission energies of the Kβ1,3, Kβ″, and Kβ2,5 peaks are discussed using m.o. theory. The Kβ″ : Kβ2,5 relative intensity is much higher than for comparable main-group compounds; this is probably due to the presence of 3p character in the orbital that gives rise to Kβ″; 3p character also enhances the intensity of Kβ2,5. Changes in peak positions and relative intensities associated with the oxidation state of vanadium can be qualitatively rationalised by a consideration of 4p character alone. It is suggested that the Kβ‴ peak observed at higher energies (+15 eV) than Kβ2,5 is formed by relaxation of an electronically excited species (resonance radiation).

Electronic structure of SiO2. II. Calculations and results

The techniques developed by the authors have been applied to compute the electronic structure of Si${\mathrm{O}}_{2}$ in the $\ensuremath{\alpha}$-quartz structure by using various clusters of different sizes. The calculated valence-band structure is consistent with the results of other self-consistent-field and semiempirical molecular-orbital calculations, and with the x-ray emission and photoemission data. Among the most interesting results are the following: (i) The width of the valence band is of the order of 9 eV. (ii) The oxygen $\mathrm{sp}$ hybridization is quite small. (iii) Crossover transitions in a literal sense are negligible. (iv) A residual charge of -1.2 on oxygen indicates that the Si-O bond in Si${\mathrm{O}}_{2}$ is partly ionic and partly covalent.

Electronic structure studies of solids. IV. Physical quantities from rigorous Hartree-Fock results for lithium crystals

Quantities associated with soft X-ray emission, the work function, the pseudopotential and Compton profiles for body centred cubic (b.c.c.) and face centred cubic (f.c.c.) lithium crystals have been calculated in the Hartree-Fock approximation of Kumar, Monkhorst and Harris (Phys. Rev. B1974). The width of the occupied part of the valence band is calculated too large by about 3 eV. Combination of soft X-ray emission and work function data indicates the bottom of the valence band is at nearly the correct position. It is found that the energy dependence of the transition dipole matrix element cannot explain prepeaking below the Fermi edge of the soft X-ray line shape. A pseudopotential form factor v(q) is calculated in the on Fermi sphere approximation. Comparison with an 'experimental' pseudopotential reflects the importance of correlation effects for small q values and the correct lattice spacing for large q values.

Non-Linear Least Squares Analysis of Proton-Induced X-Ray Emission Data

AbstractA Fortran program for analysis of spectra obtained in proton induced x-ray emission spectroscopy is under development. The first version is working and some results are shown. The program uses a model which describes the physics involved in the analysis. The continuum is described by an exponentially decreasing function representing secondary electron induced bremsstrahlung and a constant approximating different Compton scattering processes. Absorption effects are also included. All parameters in the model are fitted simultaneously. About 100 test runs have been made with good results. The continuum was accurately fitted for each spectrum. Other advantages are reliability, speed, and the fact that the program is easily adaptable to a small computer with 16K memory.

Theoretical analysis of quantitative x-ray emission data. Glasses, rocks, and metals

Theoretical analysis of quantitative x-ray emission data. Glasses, rocks, and metals

Optical properties of uranium mononitride from 0 TO 74 eV

Optical constants have been obtained for polycrystalline UN from 0 to 74 eV. The lower energy data have been compared with band structure theory and higher energy data with X-ray emission data. The P IIIn level of U in UN has been set at − 24 eV and the P II level at −32 eV relative to the Fermi Energy by analysis of these data. The calculated energy loss functions —Im(ε+1) −1 and — Im(1/ε) are interpreted in terms of a combination of single electron transitions and collective oscillations.

Electron States in Ferromagnetic Iron. I. Band Properties

A new band-structure calculation is reported for the ferromagnetic state of iron, in which the exchange interaction is given particularly careful treatment. A variational procedure was used with the wave functions expanded in terms of tight-binding functions and orthogonalized plane waves. Hybridization and spin polarization of the wave functions were allowed. Correlation corrections were incorporated. The energy bands are somewhat wider than those previously published; comparison is made with photoemission and optical reflection and x-ray emission data. The calculation leads self-consistently to the observed magnetic moment. The roles of intra-atomic exchange and itinerancy in the origin of iron's ferromagnetism are discussed.

Band Structure and Fermi Surface of Beryllium

Using a self-consistent potential, the energy eigenvalues along the symmetry edges, on the zone faces, and at the equivalent of 5184 general points in the first Brillouin zone were calculated for beryllium by expanding the conduction electron wave functions in a linear combination of 23 orthogonalized plane waves. From this the Fermi energy and density of states were calculated and the Fermi surface constructed. The density of states is in agreement with soft x-ray emission and absorption data and with the experimental low-temperature specific heat coefficient. The Fermi surface consists of three pieces: A region of unoccupied states in the first double zone which resembles a coronet, and two identical pockets of electrons in the second double zone similar in shape to a cigar with a triangular cross section. The de Haas-van Alphen frequencies in $\frac{1}{H}$ predicted from the Fermi surface are in good agreement with those measured experimentally.

Atomic level energies in hafnium

>The photoelectron method for obtaining electron binding energies is described. The method was applied to the L/sub I/, L/sub II/, and L/sub III/ levels in hafnium. The Hf K alpha /sub 1/ and Hf K alpha /su b 2/ x-ray emission lines were measured with a crystal spectrometer. The electron binding energies of the K to O/sub III/ shells in hafnium were obtained from photoelectron and x-ray emission data. A type of Moseley diagram is described and is demonstrated for the K and L levels in the Z region 57 to 75. From these diagrams accurate binding energies for the element Pm (Z = 81) were obtained by interpolation. (auth)

LXXIX. Energy band shapes and band widths in metals

Abstract The density of states curve given by the recent theory of Bohm and Pines is compared with those of the Sommerfeld and Hartree-Fock theories. It is found that the Bohm and Pines curve shows a rudimentary ‘tail’, and the effect of this on the interpretation of the experimental soft x-ray emission data is discussed, with particular reference to the metals sodium, magnesium and aluminium. Although the Bohm and Pines band width is a great improvement on that of the Hartree-Fock theory, it is still much larger than the observed width. It is suggested that this may be partly due to the neglect of the short-range correlation energy: a lower bound to the narrowing of the band from this cause is calculated, and found to be 0·1 ev for sodium.

The soft X-Ray levels of iron, cobalt, nickel and copper

1. In a previous paper the writers showed that a considerable number of discontinuities which had been detected in the excitation of the soft X-rays from these elements by the photo-electric method could be arranged on the assumption that they were due to transitions from two levels not far from the M I and M II III , as these had been deduced from hard X-ray emission data, and a series of virtual levels falling, with a close approximation into a Rydberg series. The present paper is an attempt to arrange the remaining discontinuities which have been observed into the same scheme. Although the identity of a level formerly referred to as A with the hard X-ray M I level and of the higher level with M II III seems probable ultimately, it is not certain, and we do not wish to be dogmatic about it, so that for the present we shall refer to these levels provisionally as X 1 and X 2 respectively.