KLL Auger Spectra Research Articles

Effects of relativity on the KL1L2(3P0) Auger transition rate of 65159Tb

Abstract The KLL Auger spectrum of 65 159 Tb from the 66 159 Dy decay and, separately, its KL 1 L 2 doublet have been measured at an instrumental resolution of 33 and 20 eV, respectively, using a combined electrostatic spectrometer. Energies and relative intensities of the nine individual KLL transitions have been determined and compared with the theoretical results. The accurate value of 0.53(2) obtained for the KL 1 L 2 ( 3 P 0 ) ( 1 P 1 ) intensity ratio proved the strong influence of the effects of relativity on the KL 1 L 2 ( 3 P 0 ) transition predicted by the relativistic calculations in intermediate coupling with configuration interaction. In addition, an energy of 57995(3) eV has been determined for the nuclear transition in 159 Tb by means of our measured energy of 5999.0(25) eV for the K-58 conversion line.

Initial and Final State Effects in the Photoelectron and Auger Spectra of Si and Al Bonded in Zeolites

The dependence of the core level binding energies, Eb, of Si, Al, and O bonded in zeolites on the concentration of skeletal Al is investigated. The line shape changes of Al KLL Auger spectra appear...

The predicted influence of relativistic effects on the KL1L2(3P0) Auger transition intensity of thulium proved

The KLL Auger spectrum of thulium from 169Yb decay has been analysed at an instrumental resolution of 13 eV using a combined electrostatic spectrometer. Energies and relative intensities of the individual KLL transitions have been determined and compared with calculations. A reliable value of 0.67(5) for the KL1L2(3P0)/(1P1) transition intensity ratio obtained from our partly resolved KL1L2 doublet proved, for the first time, a sharp increase of the KL1L2(3P0) intensity in the high Z region due to the relativistic effects predicted by relativistic calculations in intermediate coupling with configuration interaction. For the first time, a broadening of the KLL Auger lines, probably due to the two different excitation ways of the 169Tm atoms in 169Yb decay (K-internal conversion and K-electron capture), has been observed. A value of 19.5(8) eV was obtained for the energy separation of the two thulium KLL Auger spectra shifted to each other, arising from the individual excitation modes, and that of 0.81(9) for their intensity ratio (`K-conversion' to `K-capture'). © 1997 Elsevier Science B.V.

An experimental investigation of the relativistic effects on the KL1L2(3P0) Auger transition rate of 131Xe

Abstract The KLL Auger spectrum of 131 Xe from the 131 Cs decay has been measured at an instrumental resolution of 13 eV. Energies and relative intensities of the individual KLL lines here been determined and compared with the theoretical results. Our KL 1 L 2 ( 3 P 0 )/( 1 P 1 ) intensity ratio of 0.33(2) agrees remarkably well with that of 0.34 from the relativistic calculations in intermediate coupling with configuration interaction. This agreement clearly proves the predicted strong influence of the effects of relativity on the KL 1 L 2 ( 3 P 0 ) rate even at Z =54, since the relative intensity KL 1 L 2 ( 1 P 0 )/( 1 P 1 ) has been found to be exceedingly sensitive to these effects.

Intensities and angular distribution parameters for the KLL Auger transitions of atomic oxygen

The energies, intensities and the angular anisotropy coefficients of Auger electrons have been calculated for the KLL Auger spectra of free oxygen atoms. For open shell atoms an anisotropic Auger emission can appear even for the KLL Auger lines. To study the oxygen KLL Auger spectra we calculated the Auger matrix elements within the multiconfigurational Dirac - Fock model using the intermediate coupling scheme for representing the atomic states. The energies, intensities and angular distribution parameters are discussed together with theoretical predictions in the LS coupling and are compared to recent experimental and theoretical results. We also discuss the influence of overlapping initial fine structure states on the Auger dynamics. Large anisotropy coefficients in conjunction with large intensities are predicted for a coherently excited initial and unresolved final state fine structure. It is suggested that the angular distribution of the Auger line is measured.

The KLL and KLM Auger spectra of 3 d transition metals, Z = 23–26

High resolution (1.0–1.6 eV) X-ray excited KLL and KLM Auger spectra and the respective Auger parameters of V, Cr, Mn and Fe, obtained from thin metallic layers, are reported. The corresponding experimental (Auger) transition energies (the first high resolution experimental data except for Mn) and relative Auger intensities are compared with data obtained earlier following electron capture in the decay of radioactive isotopes, and also with available theoretical estimates. Differences in the surface chemical states of the samples and in the methods applied for evaluation of the spectra could explain the considerable deviations between the two sets of experimental results, rather than differences in the Auger process following photoionization and electron capture. The number of Auger transitions identified in the KLL spectra shows the applicability of the intermediate coupling model for these cases.

On the formation of hollow atoms in front of an insulating LiF surface

KLL Auger spectra of hydrogenic (1s) N, O and Ne ions impinging on an insulating LiF(100) single crystal are presented. Beam energy and incident angle have been varied such that the lowest possible velocity towards the target is achieved, at the same time varying the velocity parallel to the target by a factor of 10. Similarities and differences between the LiF spectra and spectra measured on (semi) conducting Si(100) and Al(110) surfaces are discussed.

Soft X-ray resonant raman and resonant Auger spectra in Si K absorption edge

Si KLL Auger spectra and Kα x-ray emission spectra of Si and SiO 2 excited at the incident photon energies around the Si K edge were measured. For Si, evolution of the Auger spectra across the K edge and that of the Kα emission spectra are apparently the same. While for SiO 2, a distinct difference between evolution of the Auger spectra and that of the x-ray emission spectra is found, i.e. no x-ray emission peak showing linear dispersion is observed above the edge.

Absolute Auger rates, relative intensities and angular distribution for the KLL spectra of Auger electrons from laser-excited sodium

The absolute Auger rates, relative intensities and the angular anisotropy coefficients of Auger electrons have been calculated for the KLL Auger spectra of laser-excited sodium atoms. Where in closed-shell atoms the KLL Auger lines have to be isotropic this is no longer valid for certain Auger transitions in open-shell systems. To study the KLL Auger spectra of excited sodium atoms we calculated the Auger matrix elements within the multiconfigurational Dirac - Fock model using the intermediate coupling scheme for representing the atomic states. The intensities and angular distribution parameters are discussed together with theoretical predictions in the LS coupling and compared to results obtained for the sodium ground-state KLL Auger transitions. We also discuss the influence of overlapping initial fine-structure states on the Auger dynamics. Large anisotropy coefficients are predicted, even for the case of a non-resolved initial- and final-state fine structure. .

Conjugate shake-up-enhanced Auger transitions in N2.

A substantial enhancement of intensity in the high-energy part of the ${\mathrm{N}}_{2}$ KLL Auger spectrum has been observed at photon energies a few tens of eV above the N 1s threshold. By monitoring the corresponding 1s photoelectron spectrum, we show that the effect is due to the emergence of strong conjugate shake-up satellites. As shown in previous e-2e studies for CO, such Auger spectra are useful in determining the intensity behavior of shake-up satellites in the immediate threshold regions.

Do hollow atoms exist in front of an insulating LiF(100) surface?

First measurements of KLL Auger spectra arising from collisions of N6+ ions on an insulating LiF(100) surface are presented. The beam energy is varied from 0.08 up to 16 keV. The incident angle is chosen such that the perpendicular velocity component is constant over the indicated energy range. Spectral features arising from above surface KLL emission, observed during interaction of N6+ with a conducting Si(100) surface, are absent for LiF, implying pronounced differences in the dynamics governing the above-surface neutralization and deexcitation of the highly charged projectiles.

Velocity dependence of KLL Auger emission from hollow atoms formed during collisions of hydrogenic N6+ ions on surfaces.

This paper presents a detailed description of KLL Auger spectra arising from collisions of hydrogenic ${\mathrm{N}}^{6+}$ ions on clean Si(100) and Al(110) surfaces at energies ranging from 78 eV up to 60 keV and at incident angles from 2.5\ifmmode^\circ\else\textdegree\fi{} up to 45\ifmmode^\circ\else\textdegree\fi{}. Atomic structure calculations of KLL Auger energies and decay rates for hollow atoms, together with simulations of the projectile trajectories, support a model in which the de-excitation of the ions proceeds essentially via two mechanisms. Before the ion enters the ``close collision range,'' a few of its L-shell vacancies are filled by Auger cascades involving outer shell electrons. But as seen as the projectile suffers close collisions, L-shell vacancies are rapidly filled by direct capture of target core electrons. The time scale of the latter mechanism is determined by the collision frequency.

Changes in oxygen Auger spectra induced by potassium in the Ni(100)-O/K coadsorption system

Adsorption of potassium on an oxygen-covered Ni(100) surface produces changes in the O KLL lineshape at all oxygen sub-monolayer coverages. The observed change is clearly K-coverage dependent. It is known that the O KLL Auger spectrum of chemisorbed oxygen is predominantly atomic-like with a band-like feature appearing at higher kinetic energy. The main effect induced by a gradually increased potassium coverage is a decrease in the intensity of this band-like structure. This result can be ascribed to an increase in the ionic character of the chemical bonding of the oxygen. On the other hand, the energies and relative intensities of the lines in the atomic-like part of the spectrum are substantially unchanged.

Angular distribution in the 1 s → 3 p coherently excited resonant KLL Auger spectrum in neon

Angular anisotropies, energies, and relative intensities have been studied for the 1 s → 3 p resonant KLL spectrum in neon. The resonant excitation of the 1 s2 p 22 p 63 p configuration leads to a multiplet of four levels with J = 0, 1, 2, and an energy splitting ≤ 35 meV which is much smaller than the natural level widths of about 250 meV. Thus, the various states of the multiplet are excited (more or less) coherently. To obtain the angular distribution of the Auger lines, knowledge of the density matrix is required. This matrix includes all information about the specific excitation process, whereas the dynamics of the autoionization is described by the relative intensities and Auger angular parameters A 2. Multiconfiguration Dirac-Fock wave functions have been used to calculate this set of coefficients in an intermediate coupling scheme including initial and final state correlations. The use of these data in the interpretation of an angular distribution measurement is briefly discussed.

X-ray excited KLL and KLM Auger spectra of manganese

High resolution ( ΔE < 1.5 eV) manganese KLL and KLM Auger spectra, obtained by photoexcitation, are persented, and the transition energies and intensities are compared with the experimental and theoretical data published earlier. Significant disagreement can be observed between the respective experimental intensity values in the cases of the most intense lines, and large differences are found between the experimental and the available theoretical transition energy values of the main peaks. The disagreements between the experimental data can be explained rather by the different chemical states of the manganese samples investigated in the separate experiments than by the different mechanisms of the Auger processes.

Damaging process of graphite and diamond studied by Auger electron spectroscopy and laser Raman spectroscopy

In order to examine the changes of electronic structure in graphite irradiated with Ar ions and electrons, an in-situ Auger electron spectroscopic (AES) analysis has been carried out. Under the irradiation of 3 keV Ar ions and/or electrons, the carbon KLL (C-KLL) Auger spectra of a highly oriented pyrolytic graphite (HOPG) and a diamond were measured precisely and compared with those of unirradiated carbon materials having various crystallinity. On Ar irradiation, the C-KLL spectra of both HOPG and diamond are markedly changed to a very similar structure which is stable for further heavy irradiation, and is considered to correspond to an amorphization by the displacement effect of the incident Ar ions. The electron bombardment also causes some spectra changes but does not amorphize the graphite. This means that the graphite structure is also modified by the electronic excitation. Comparing the detailed changes in the C-KLL spectra by the bombardment with those observed in laser Raman spectroscopic analysis, the electronic as well as crystallographic changes in the damaging process of the irradiated graphite are discussed.

Coster-Kronig transitions in hollow atoms created during highly charged ion-surface interactions.

We present high resolution KLL Auger spectra emerging from collisions of H-like and metastable He-like C, N, and O on a B-doped Si(100) surface. In combination with the high resolution electron spectroscopy, Hartree-Fock calculations allow us to succesfully identify KLL Auger electrons arising from specific states that form a part of the autoionization cascade as the multiply excited projectiles deexcite. We find strong evidence for Coster-Kronig transitions taking place in the hollow atoms which give rise to missing peaks in the Auger spectra.

Absolute Auger rates, relative intensities and angular distribution of the KLL spectra of Auger electrons from alkali atoms

The absolute Auger rates, relative intensities and the angular anisotropy coefficients of Auger electrons have been calculated for the KLL Auger spectra of the alkali atoms Na, K, Rb, and Cs. Where in closed-shell atoms the KLL Auger lines have to be isotropic, this is no longer valid for certain Auger transitions in open-shell systems. The angular anisotropy coefficients are calculated for open-shell atoms for the first time applying an intermediate coupling scheme. The relativistic multiconfigurational Dirac-Fock model including Breit-QED and exchange interaction is used for the calculation of the Auger matrix elements. The results for the Auger rates and intensities are compared with earlier theoretical predictions and experimental data. The angular anisotropy parameters are discussed together with theoretical predictions in the LS coupling. Large angular anisotropy coefficients have been found for the KL1L2.3 Auger transitions of all alkali atoms. In particular, an observable angular anisotropy can be predicted for the Auger transitions of potassium.

Local electronic structures in phosphorus oxyanions

AbstractThe local electronic structure around the core‐ionized phosphorus and oxygen atoms in solid phase Na3PO4, (NaPO3)n and Li3PO4 compounds has been studied by XPS and x‐ray excited Auger spectroscopy. Core level and valence band photoelectron spectra, as well as the O KLL Auger spectra have been measured using monochromated Al Kα excitation, while the high energy P KLV spectra have been excited using Mo‐x‐rays.From the similarity of the structures of the P KLV spectra it can be seen that the effect of the common tetrahedral symmetry is dominant while the effect due to the change of the cation is much smaller. This observation is supported by comparing the respective valence band photoelectron spectra to each other, and to the results obtained from cluster MO calculations.From the evaluation of the O KVV and O 1s spectra the oxygen Auger parameters have been derived and the 2p2p and 2s2p hole repulsion energies have been determined for each compound. The experimental values of the different Auger parameter shifts (Δα′, Δβ′) place the three oxyanions into the class of oxides, hydroxides and metallic anions instead of the class of non‐metallic anions and indicates the low electronic polarizability (similar to that of SiO2) of these phosphorus oxyanions.

Amorphous Boron Carbide by AES

The Auger electron spectra for amorphous boron carbide (B4C) are presented. The first derivative C KLL Auger electron spectrum of a crystalline carbide exhibits a peak shape different from that of adventitious hydrocarbon. The peak shape of the C KLL spectrum for a carbide such as TaC contains three components present at the approximate kinetic energies of 250, 260, and 270 eV, with the peak at 270 eV having a greater intensity in the positive direction than the C KLL spectrum for adventitious hydrocarbon. The features exhibited in the differentiated C KLL Auger spectrum for amorphous B4C are similar, but not identical to other metal carbides and are characteristically different from adventitious hydrocarbon, graphite, SiC, and other metal carbides.