Spectroscopy AES

Naiiow-line uv—vis spectia of free atoms, corresponding to transitions ia the outer electron shells, have long been employed for elemental analysis usiag both atomic absorption (AAS) and emission (AES) spectroscopy (159,160). Atomic spectroscopy is sensitive but destmctive, requiring vaporization and decomposition of the sample iato its constituent elements. Some of these techniques are compared, together with mass spectrometry, ia Table 4 (161,162). 

XPS and AES spectroscopies. The other group reported that the tribofilms were inorganic amorphous phosphates, mainly orthophosphate (P043), and pyrophosphate (P2074) associated with zinc and magnesium from hard-core RMs. Tribofilms were low in sulfur, being present mostly as a sulfide. 

Characterization of the bearing surface film, and film formed in a lubricated cam/tappet friction apparatus have been analyzed by reflectance-absorption infrared, X-ray photoelectron (XPS) and Auger electron (AES) spectroscopies (Lindsay et al., 1993). The two lubricants used were similar to fully formulated engine oils. 

The abrasivity of surfaces is related to the shape of surface profiles and can be described numerically. The morphology of wear particles, in terms of their shape, size, and surface texture, reflects the complex nature of the wear process involved in particle formation (Stachowiak, 1998 and 2000 Stachowiak and Podsiadlo, 1999 and 2001). The cumulative evaluation of turbine lubricating oil system, using techniques such as automatic particle counters, ferrography, ICP-AES spectroscopy, and scanning electron microscopy indicated the involvement of very small iron particles in the size range of 1-10 microns or less, and abrasive wear silica particles in the size range of 10-40 microns (Korycki and Wislicki, 1991). 

AES ARABS Auger electron spectroscopy [77, 112-114, 117] Angle-resolved AES [85, 115] An incident high-energy electron ejects an inner electron from an atom an outer electron (e.g., L) falls into the vacancy and the released energy is given to an ejected Auger electron Surface composition... 

APS Appearance potential spectroscopy (see AES) Intensity of emitted x-ray or Auger electrons is measured as a function of incident electron energy Surface composition... 

Electronic spectra of surfaces can give information about what species are present and their valence states. X-ray photoelectron spectroscopy (XPS) and its variant, ESC A, are commonly used. Figure VIII-11 shows the application to an A1 surface and Fig. XVIII-6, to the more complicated case of Mo supported on TiOi [37] Fig. XVIII-7 shows the detection of photochemically produced Br atoms on Pt(lll) [38]. Other spectroscopies that bear on the chemical state of adsorbed species include (see Table VIII-1) photoelectron spectroscopy (PES) [39-41], angle resolved PES or ARPES [42], and Auger electron spectroscopy (AES) [43-47]. Spectroscopic detection of adsorbed hydrogen is difficult, and... 

A popular electron-based teclmique is Auger electron spectroscopy (AES), which is described in section Bl.25.2.2. In AES, a 3-5 keV electron beam is used to knock out iimer-shell, or core, electrons from atoms in the near-surface region of the material. Core holes are unstable, and are soon filled by either fluorescence or Auger decay. In the Auger... 

AES Auger electron spectroscopy After the ejection of an electron by absorption of a photon, an atom stays behind as an unstable Ion, which relaxes by filling the hole with an electron from a higher shell. The energy released by this transition Is taken up by another electron, the Auger electron, which leaves the sample with an element-specific kinetic energy. Surface composition, depth profiles... 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

ICP/AES. inductively coupled plasma and atomic-emission spectroscopy used as a combined technique... 

If the radiofrequency spectmm is due to emission of radiation between pairs of states - for example nuclear spin states in NMR spectroscopy - the width of a line is a consequence of the lifetime, t, of the upper, emitting state. The lifetime and the energy spread, AE, of the upper state are related through the uncertainty principle (see Equation 1.16) by... 

For inductively coupled plasma atomic emission spectroscopy (ICP-AES) the sample is normally in solution but may be a fine particulate solid or even a gas. If it is a solution, this is nebulized, resulting in a fine spray or aerosol, in flowing argon gas. The aerosol is introduced into a plasma torch, illustrated in Figure 3.21. 

A wider range of elements is covered by ICT-AES than by atomic absorption spectroscopy. All elements, except argon, can be determined with an inductively coupled plasma, but there are some difficulties associated with He, Ne, Kr, Xe, F, Cl, Br, O and N. 

Figure 8.1 Processes occurring in (a) ultraviolet photoelectron spectroscopy (UPS), (b) X-ray photoelectron spectroscopy (XPS) and (c) Auger electron spectroscopy (AES)...

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