Solid state broadening in Auger spectra

Some Auger spectra in the gas phase show extremely sharp lines and a great deal of fine structure while the Auger spectra of solids, even at high resolution, lack this detailed fine structure and generally have much broader peaks. In an effort to understand the broadening processes which occur on condensation of a gas or vapour to the solid phase, several solids for which high resolution gas phase data exists have been studied. The result of measurements of the M₄₅N₄₅N₄₅ Auger spectrum of cadmium are reported and comparison is made with the vapour phase data. Although the solid data contains considerable quasi-atomic fine structure the lines are broader than the vapour phase and by matching computer broadened vapour phase data to the experimental data an estimate of the individual line widths may be made. The relative intensities of the lines in the simulation agree closely with the solid data if loss processes are considered. Measurements have also been made on the same Cd transition in CdS and in this material the Auger lines are much broader than in Cd metal and the fine structure has almost disappeared. Results are also reported of measurements of the Auger spectra of solid rare gases made with the aid of a UHV cryostat capable of operating at temperatures down to 10 K. The gases studied were Xe, Ar and Kr and again comparison with computer broadened gas data enable the broadening of individual Auger lines to be estimated. Measurements of the line breadths have been made at various temperatures and the results of these experiments will be discussed in terms of lifetime and lattice vibrational broadening.     

Auger spectra of lithium hydride

Auger electron emission spectra have been observed for lithium hydride in three conditions : (1) cleaved in vacuum, (2) prepared by the reaction of hydrogen gas with clean lithium metal, and (3) by annealing slightly oxidized lithium hydride single crystals in vacuum. The dominant Auger line (40 ± 1 eV) was found to be a KVV transition involving valence electrons from the anion and was indistinguishable from a similar transition for lithium oxide at room temperature. Lithium hydride surfaces lose hydrogen in vacuum causing the formation of a lithium metal phase at room temperature and a significant reduction in surface hydride stoichiometry at 600°C.     

The Auger spectra of uranium

TheL, M, andK-Auger andL-Coster-Kronig spectra of uranium were measured and are compared to other experimental and theoretical work. The meanL-shell fluorescence yield of uranium was measured as \(\bar \omega _L \) =0.53±0.06.      

Rule of corresponding Auger spectra

The normalized core-valence-valence Auger spectra A(?) of the simple metals Be, Mg, and A$\text{l}$, when plotted as a function of ?/2λ, where λ is the free-electron Fermi energy, are all nearly the same. Li, with λ=4.1±0.1 eV, also has the same spectrum. This suggests that the Auger spectra of simple metals depend primarily on the electron gas density and are almost independent of details of the band structure.     

Excitation lines and multiple ionization in Auger spectra

Satellite lines of a new type and excessively large continuous distributions of energy degraded electrons are observed in theKLL Auger spectra of potassium, chlorine, and sulfur. The lines are tentatively interpreted as due to a process that is characteristic of the atom more than of the entire solid and the excessive number of electrons in the continuous distributions is interpreted as due to multiple ionization.     

X-ray excited Auger and photoelectron spectra of partially oxidized magnesium surfaces: The observation of abnormal chemical shifts

A comparison of the spectra of metals and their oxides reveals large differences between the chemical shifts in Auger and photoelectron lines. The data for magnesium are discussed in detail. An explanation is proposed which is based upon the difference in polarization energy between the double-hole state produced by the Auger electron emission and the single-hole state which results from the photoelectron emission.     

Auger and emission spectra of carbon nanotubes

The Auger and x-ray emission spectra of carbon nanotubes are calculated by the FP-LMTO method. The computed spectra for nanotubes are compared to the analogous spectra for a graphite monolayer, which is used as a test object, and to the experimental curves for graphite. It is concluded that the Auger-characteristic emission can be used to identify carbon nanotubes. Fiz. Tverd. Tela (St. Petersburg) 41, 1511–1514 (August 1999)     

Energy parameter and the free-atom behavior of Auger spectra

The L₃M₄₅M₄₅ spectra of V and Cr do not exhibit free atom behavior, in sharp contrast to those of Cu and Zn. An energy difference parameter, Δ ?, derived entirely from observable energies, has been introduced to correlate with the extent of electron localization and free-atom behavior in Auger transitions.     

Disorder broadening of alloy Auger spectra

Auger spectroscopy promises the means to separate initial and final state contributions to the disorder broadening of core XPS spectra in disordered alloys. Auger disorder broadening, deduced from recent ab initio results, is predicted to be greater than XPS disorder broadening for Cu₅₀Pd₅₀ and Ag₅₀Pd₅₀ alloys. Simulations are used to assess whether this effect is observable experimentally despite the greater lifetime broadening of Auger spectra. A number of cases where narrow core–core–core Auger transitions should allow clear experimental identification of this effect are identified. The prospects for determining environment-resolved Auger spectra using APECS have been investigated.     

TheL- andK- Auger spectra of tellurium

TheL- andK- Auger spectra of tellurium (Z=52) were studied from the electron capture decay of¹²⁵I. The measured relativeL- Auger transition intensities are not in agreement with the theoretical intensities of Asaad for silver (Z=47). The measured relativeKLL intensities are in agreement with those ofGraham et al. Relative intensities are given for theKL Y spectrum. TheKL Y/KLL ratio was measured to be 0.44 ± 0.02 in good agreement with the theoretical value given byWapstra.K/L andL subshell conversion ratios are given for the 35 keV nuclear transition in¹²⁵Te.     

Radiative Auger emission in Ne K X-ray spectra

Radiative Auger emission intensity in K X-rays from neon was measured following electron bombardment by 1 to 2 keV electrons. The measured relative intensities of this process are in good agreement with calculations of Dyall using correlated final-state wavefunctions.     

High energy satellites in Auger spectra from metals

Auger spectra from Mg and Li suggest that the high energy satellites observed in some metals are due to double ionization rather than to a coupled plasmon-hole excitation.     

New feature in the Auger peak of adsorbed oxygen

Recent joint theoretical and experimental investigations of Auger core-core-valence spectra of alkali adatoms on simple metals have revealed that such technique is capable to ascertain contributions from different adsorption environments in the signal [M.I. Trioni, S. Caravati, G.P. Brivio, L. Floreano, F. Bruno, A. Morgante, Phys. Rev. Lett. 93 (2004) 206802]. Consequently, to verify if such an effect is present also for other chemical species, we study theoretically the KLV transition of oxygen either as a bulk impurity or as an adsorbate in/on Al and Ag (jellium-like). We make use of the Fermi golden rule in which the matrix elements of the interaction are calculated within DFT. We verify that the relevant physical quantity of this phenomenon is the excited local density of states (LDOS), calculated within a region centered on the core ionized atom. The Auger rate for oxygen in Ag bulk displays a single asymmetric peak, while for adsorbed oxygen a second smaller feature at lower energies, and very close to the first one, appears. This unexpected result follows from the removal of the degeneracy of the m quantum number of the 2p states of oxygen at the surface. It is only displayed on the electronically less dense metal (Ag), but not on Al.     

Two hole resonances in the XVV Auger spectra of solids

A theory of XVV Auger spectra of atoms in solids is proposed, that takes hole-hole repulsion into account. The interaction between the holes is taken to be localized at the atomic site. Within this model, the theory is exact. The relationship between atomic-like and band-like spectra is discussed and several previously unexplained features of the experimental spectra are shown to find a natural justification within the context of the theory.     

Quasi-atomic fine structure in the Auger spectra of solid silver and indium

High resolution M₄,₅N_4,5N_4,5 Auger spectra of Ag and In reveal fine structure, which may be interpreted in terms of spin-orbit splitting of the initial state and multiplet structure in the final state. Interaction between d holes in Ag is an important factor in determining the shape of the Auger spectrum, and so the Auger profile is not related in any simple way to the one-particle density of states.     

Correlation effects in Auger spectra of Ni and Cu nanoclusters

Results of experimental research of exciton-like two-hole states in nanoclusters of narrow-band metals (Ni, Cu) on surface of high-oriented pyrolitic graphite by X-ray photoelectron and Auger electron spectroscopy are presented. It was found that the evolution of the electronic structure in Ni nanoclusters with the decreasing of their sizes can lead to appearance of long-living two-hole states in the valence band. One-particle and two-particle density of states are analyzed, and the Auger-electron spectra confirming the presence of the bound and localized states are obtained.