Energies, Auger

The availability of high-intensity, tunable X-rays produced by synchrotron radiation has resulted in the development of new techniques to study both bulk and surface materials properties. XAS methods have been applied both in situ and ex situ to determine electronic and structural characteristics of electrodes and electrode materials [58, 59], XAS combined with electron-yield techniques can be used to distinguish between surface and bulk properties, In the latter procedure X-rays are used to produce high energy Auger electrons [60] which, because of their limited escape depth ( 150-200 A), can provide information regarding near surface composition. 

Fain and McDavid (16) measured the surface composition of Ag-Au alloys with low-energy Auger electrons. The surface concentration proved to be linear and the work function nonlinear in the bulk concentration. This clearly shows that a deviation from linearity of the work function is in itself no proof of surface enrichment. 

Local Electronic Structures from Analyzing and Modeling High-Energy Auger and Photoelectron Spectra of Solids... 

Plenary 2. Laszlo Kover (Institute of Nuclear Research of the Hungarian Academy of Sciences) Local Electronic Structures from Analyzing and Modeling High Energy Auger and Photoelectron Spectra of Solids... 

The low kinetic energy Auger A1 KLL component line in the Na-mordenite and Na-ZSM-5 samples have not being assigned. We will come back to this result when we discuss acidic sites in high silica zeolite. 

Their total concentration would therefore be essentially proportional to the external surface area of the crystals. Similar surface A1 atoms may be responsible for the low kinetic energy Auger peaks observed in Rgure 12 for high silica zeolites. In this case the sodium cation instead of the proton would be adjacent to the silanol group. 

Figure 1. Low energy Auger spectra for the iron sulfides.

Indeed, competing non-radiative processes are present in the decay of the excited state. They correspond to Auger transitions in the excited atom and high energy Auger lines appear in the corresponding nl spectrum 14). 

Two-step autoionisation may be regarded as the lowest energy Auger effect it sets in as one crosses the double-ionisation threshold towards higher energies. 

AES is primarily a surface elemental analysis technique. It is used to identify the elemental composition of solid surfaces, and can be used to quantify surface components, although quantitative analysis is not straightforward. AES is a true surface analysis technique, because the low-energy Auger electrons can only escape from the first few (three to five) atomic layers or from depths of 0.2-2.0 nm. 

The nature of the complexes formed between water, methanol and ethanol molecules and Co cations was determined [24]. A large anomalous ferric component was observed in the spectra of the water-complexed sources but not with the alcohol-complexed sources. This ferric component arose from the radiolysis of the complexed water molecules in the electron capture decay process of Co. Following the electron capture the water in the first coordination sphere of the MSssbauer atom is subjected to a flux of low energy Auger electrons and X-rays. This water is decomposed into H and OH radicals and it is the H radicals that can oxidize the Fe " to Fe +. Interestingly, no anomalous Fe component was observed when methanol or ethanol was the sorbate. Irradiation of alcohols does not lead to the production of alkoxide radicals. 

One more qualitative verification of the necessity of allowance for the second-order processes in the formation of fine structure above the CVV Auger lines is the oscillating structures above the high-energy Auger lines. 

As a result of the photoionization, a singly ionized atom is formed, which can also be produced by electron impact. The core hole (eg, in the K shell) can be filled by an electron from a higher shell (eg, the Li shell) and the energy of this de-excitation process can be released by emission of an X-ray photon (X-ray fluorescence, XRF) or can be transferred to another electron (eg, in the L2 shell), which is then emitted with a well-defined kinetic energy (Auger process). This... 

LMM Low energy Auger electrons 0,6 keV (-60%) - LEEMS (<5 nm) MMM Low energy Auger electrons <0.1 keV LEEMS) Shake-off very low energy energy electrons -10 eV - LEEMS... 

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