The past, present, and future of auger line shape analysis

Ramaker, David E.

doi:10.1080/10408439108243752

Cited by 107 publications

(49 citation statements)

References 304 publications

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“…In general, the features of the O KLL-Auger electron spectrum can be grouped into 3 regions that can be assigned to different transitions of the participating electrons in the Auger process. [58] A simple term scheme explaining the details is shown as Fig. 12 B.…”

Section: In-situ Photoelectron Spectroscopymentioning

confidence: 99%

Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid

Hävecker

Wrabetz

Kröhnert

et al. 2012

Journal of Catalysis

162

183

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The surface of a highly crystalline MoVTeNb oxide catalyst for selective oxidation of propane to acrylic acid composed of the M1 phase has been studied by infrared spectroscopy, microcalorimetry, and in-situ photoelectron spectroscopy. The acid-base properties of the catalyst have been probed by NH3 adsorption showing mainly Brønsted acidity that is weak with respect to concentration and strength of sites. Adsorption of propane on the activated catalyst reveals the presence of a high number of energetically homogeneous propane adsorption sites, which is evidenced by constant differential heat of propane adsorption qdiff,initial=57 kJ mol -1 until the monolayer coverage is reached that corresponds to a surface density of approximately 3 propane molecules per nm 2 at 313 K. The decrease of the heat to qdiff,initial=40 kJ mol -1 after catalysis implies that the surface is restructured under reaction conditions. The changes have been analyzed with high-pressure in-situ XPS while the catalyst was working applying reaction temperatures between 323 and 693 K, different feed compositions containing 0 mol.-% and 40 mol.-% steam and prolonged reaction times. The catalytic performance during the XPS experiments measured by mass spectrometry is in good agreement with studies in fixed bed reactors at atmospheric pressure demonstrating that the XPS results taken under operation show the relevant active surface state. The experiments confirm that the surface composition of the M1 phase differs significantly from the bulk implying that the catalytically active sites are no part of the M1 crystal structure and occur on all terminating planes. Acrylic acid formation correlates with surface depletion in Mo 6+ and enrichment in V 5+ sites. In presence of steam in the feed, the active ensemble for acrylic acid formation appear to consist of V 5+ oxospecies in close vicinity to Te 4+ sites with an element ratio Te/V=1.4. The active sites are formed under propane oxidation conditions and are embedded in a thin layer enriched in V, Te, and Nb on the surface of the structural stable self-supporting M1 phase.

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Section: In-situ Photoelectron Spectroscopymentioning

confidence: 99%

Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid

Hävecker

Wrabetz

Kröhnert

et al. 2012

Journal of Catalysis

162

183

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“…Ramaker has discussed the various mechanisms to which it has been attributed. 47,48 It can be easily shown that most of the Auger electrons detected in coincidence are emitted from the first few atomic layers. While there may be non-stoichiometric oxide in the near-surface region which may be expected to make a stronger relative contribution in the more surface sensitive APECS spectrum, our preferred interpretation of the shoulder is that it arises as a consequence of final-state correlation effects according to a model proposed to explain O K-LL AES lineshapes.…”

Section: Recent Results the Coincidence O K-l 23 L 23 Auger Spectrumentioning

confidence: 99%

“…46 In terms of the Cini-Sawatzky (CS) theory, there are delocalised final states in which the two valence holes are in different Si-O-Si bonding orbitals and the hole-hole interaction energy is reduced, giving rise to the high-energy shoulder. 48 To investigate the Auger lineshape and the enhancement of the shoulder in the APECS spectrum, we compared the coincidence spectrum to a model CS lineshape. We used O 2p densities of states (DOS) calculated for different sites on a Si 8 O 7 cluster.…”

Section: Recent Results the Coincidence O K-l 23 L 23 Auger Spectrumentioning

confidence: 99%

Auger photoelectron coincidence spectroscopy: simplifying complexity

Riessen

Thurgate

2006

Surface & Interface Analysis

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The use of X-ray photoelectron spectroscopy (XPS) is expanding rapidly with the advent of more convenient, high-resolution laboratory-based instruments. The increase in the numbers and distribution of synchrotrons has also fuelled this burgeoning interest. Powell (C. J. Powell, J. Vac. Sci. Technol. A 21 (S42) 2003) has shown that the number of papers published on or using XPS has doubled in the past 10 years. He reports that there are in excess of 3000 papers published using XPS data each year across a wide range of applications, making it the most important technique for the determination of the composition of nano-scale surface films. Yet XPS and the associated technique of Auger-electron spectroscopy (AES) are not yet developed to the stage where the data and its interpretation are unambiguous. Auger photoelectron coincidence spectroscopy (APECS) provides a means of simplifying spectra, allowing for the decomposition of these into components that have a common origin. The spectra so produced provide a unique opportunity to test theory. In this paper, we will review recent progress in developing better APECS spectrometers and illustrate the power of APECS with new data acquired by these.

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“…The first observable is related to the lifetime of the intermediate bound state and it is proportional to the linewidth, while angular distribution and momentum analysis can be exploited in electron coincidence spectroscopy experiments when the decay leads to the fragmentation of the system. In condensed matter, several processes, such as electron-phonon interactions, shake transitions and plasmon excitations, may contribute to broaden the lineshape [42].…”

Section: Basic Measurable Spectroscopic Parameters In Electron Spectrmentioning

confidence: 99%

“…Difficulties are mainly related to the theoretical and computational treatment of a large number of channels, of many-body correlations in excited states and of interchannel potentials in extended systems with reduced symmetry [14]. Therefore, while a large number of computational techniques have been successfully developed for molecular systems [29,46,47] and several total energy calculations have been carried out using standard ab initio methods for bound and excited states, this number is smaller for condensed matter, and few calculations of electron spectral lineshapes have been published [34,42,48,49].…”

Section: Basic Computable Spectroscopic Parameters In Electron Spectrmentioning

confidence: 99%

Electron spectroscopies and inelastic processes in nanoclusters and solids: Theory and experiment

et al. 2010

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The past, present, and future of auger line shape analysis

Cited by 107 publications

References 304 publications

Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid

Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid

Auger photoelectron coincidence spectroscopy: simplifying complexity

Electron spectroscopies and inelastic processes in nanoclusters and solids: Theory and experiment

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