Electron dispersive spectra

Ap, weight gain and ESEM, and electron dispersive spectra (EDS) for species detection, and (vi) filtration subsystem development and optimization. 

Electron dispersive spectra allows the selective elemental analysis of objects seen on samples while viewed with an electron microscope. This was used to examine the particulates shown in Figure 4.32. 

Critical Coagulation Concentration Chromatographable Organic Carbon Chloral Hydrate Forming Potential Disinfection By-Product Diethylaminoethyl Diffusion Limited Aggregation Dissolved O anic Carbon Dissolved Organic Matter Direct Observation through the Membrane Technique Diffusive Reflectance Fourier Transform Infrared Spectroscopy Electronic Conductive Carbon Black Electron Dispersive Spectra Ethylene Diamine Tetra Acetic Acid Fulvic Acid... 

Molecules in crystals or dispersed in host lattices are often present in a range of environments, and this results in a broadening of the electronic absorption spectrum. Such an inhomogeneously broadened absorption band (envelope of transitions) may be considered as a superposition of several distinguishable sites. A narrow line laser can saturate one of the transitions under the envelope and the corresponding molecules will no longer take part in the absorption process. This phenomenon is referred to as hole... 

Fig. 27.9. (a) Electron microscopic photo and (b) energy dispersion spectrum of working surface of transducer with inserted catalyst. 

Figure 12. Scanning electron micrograph of a liquid extrusion on infiltrated concrete removed from water and the corresponding x-ray energy dispersive spectrum showing that sulfur predominates over calcium. Globular masses erupted during evacuation.

Fig. 9.13 (a-d) Schematic view of the electron dispersion of bilayer graphene near the K and K points showing both 7ti and 7t2 bands. The four double resonance Raman scattering processes are indicated. The wave vectors of the electrons ( i, 2. and k-l) involved in each of these four processes are also indicated [27]. (e) Typical 2D band spectrum with the four components is indicated... 

A zeolite with MFI structure was synthesised with 3 different amounts of niobium ammonium complex (NAC) in the reaction mixture. The samples obtained were characterised by scanning electron microscopy (SEM) using secondary electron detector and energy dispersive spectrum (EDS) detector, X-ray diffraction (XRD), differential thermal analysis (DTA), and electron paramagnetic resonance (EPR). The increase of NAC in the reaction mixture results in the decrease of the crystal size of the zeolite. The characterisation shows evidence that the niobium was incorporated into MFI structure. 

Most single molecule experiments in solids at low temperatures described in this book have been performed using fluorescence excitation techniques in which the pure electronic absorption spectrum is monitored by detection of the total Stokes shifted fluorescence as a function of the excitation frequency. There is, however, also the possibility to excite the molecule with a fixed frequency in the maximum of its absorption line and disperse the emitted fluorescence light by a monochromator. In this fashion the vibrationally resolved fluorescence spectrum of a single molecule can be recorded. 

Electron-Dispersive Scattering (EDS) spectra obtained from several regions across the wear track indicated the presence of iron oxides, aluminum (metal and oxide) and zinc (metal and oxide). A typical EDS spectrum from the AIBC QEN4 wear surface is shown in Figure 14. Note that there is no obvious contrast in the image that defines the region containing oxidized iron and aluminum. 

Figure 14. Electron Dispersive Scattering (EDS) spectrum obtained fix>m a region of a BSE image of the wear track in AIBC GEN4 disc sample after fnction/wear test.

The electronic polarization (P ) of a molecule is not only useful to calculate the atomic component of the molar polarization and the dipole moment, but is of independent interest for studying the bonding type and structure of a substance. Among chemists the Pe determined according to Eq. 11.14 is commonly known as the refraction , R, and is expressed in non-SI units, cm /mol, whereas physicists prefer to use polarizability a, expressed in A, so that formally a = 0.3964 R (a is also expressed in atomic units, 1 a. u. = 0.148185 A ). For uniformity, is measured with the 589 nmNa line (Ru) or is extrapolated to infinitely long waves (Poo), unless the entire dispersion spectrum of RI is determined. 

We could observe aluminium and silicon in the cytoplasmic extracts of P. extenta electric tissue (Prado Figueroa et al, 2008) using a combination of scanning electron microscopy and X-ray spectrometry (EDS/SEM) (see Fig. 1). The result of this microanalysis is an energy-dispersive spectrum in which the peaks are localized at energy lines characteristic for each element... 

Modern multichannel transducers consist of an array of small photosensitive elements arranged either linearly or in a two-dimensional pattern on a single semiconductor chip. The chip, which is usually silicon and typically has dimensions of a few millimeters on a side, also contains electronic circuitry to provide an output signal from each of the elements either sequentially or simultaneously. For spectroscopic studies, a multichannel transducer is generally placed in the focal plane of a spectrometer so that various elements of the dispersed spectrum can be transduced and measured simultaneously. 

First we consider the main features of the electron energy spectrum of these compounds taking TiC as an example. Fig. 2.1 shows the dispersion curves for TiC as obtained from the self-consistent APW calculations of Neckel et al (1976). Characteristic elements of the valence-state spectrum of the carbide are the following ... 

Figure 3 Electronic dispersion in the honeycomb lattice. (Lett) Energy spectrum. (Right) Zoom of the energy bands close to one of the Dirac points. Reprinted with permission from Castro Neto, A. H. Guinea, F. Peres, N. M. R. etal. Rev. Mod. Phys. 2009,81,109. Copyright 2009 American Physical Society.

While a laser beam can be used for traditional absorption spectroscopy by measuring / and 7q, the strength of laser spectroscopy lies in more specialized experiments which often do not lend themselves to such measurements. Other techniques are connnonly used to detect the absorption of light from the laser beam. A coimnon one is to observe fluorescence excited by the laser. The total fluorescence produced is nonnally proportional to the amount of light absorbed. It can be used as a measurement of concentration to detect species present in extremely small amounts. Or a measurement of the fluorescence intensity as the laser frequency is scaimed can give an absorption spectrum. This may allow much higher resolution than is easily obtained with a traditional absorption spectrometer. In other experiments the fluorescence may be dispersed and its spectrum detennined with a traditional spectrometer. In suitable cases this could be the emission from a single electronic-vibrational-rotational level of a molecule and the experimenter can study how the spectrum varies with level. 

A multipoint ion collector (also called the detector) consists of a large number of miniature electron multiplier elements assembled, or constructed, side by side over a plane. A multipoint collector can be an array, which detects a dispersed beam of ions simultaneously over a range of m/z values and is frequently used with a sector-type mass spectrometer. Alternatively, a microchannel plate collector detects all ions of one m/z value. When combined with a TOP analyzer, the microchannel plate affords an almost instantaneous mass spectrum. Because of their construction and operation, microchannel plate detectors are cheaper to fit and maintain. Multipoint detectors are particularly useful for situations in which ionization occurs within a very short space of time, as with some ionization sources, or in which only trace quantities of any substance are available. For such fleeting availability of ions, only multipoint collectors can measure a whole spectrum or part of a spectrum satisfactorily in the short time available. 

With modern detectors and electronics most Enei -Dispersive X-Ray Spectroscopy (EDS) systems can detect X rays from all the elements in the periodic table above beryllium, Z= 4, if present in sufficient quantity. The minimum detection limit (MDL) for elements with atomic numbers greater than Z = 11 is as low as 0.02% wt., if the peaks are isolated and the spectrum has a total of at least 2.5 X 10 counts. In practice, however, with EDS on an electron microscope, the MDL is about 0.1% wt. because of a high background count and broad peaks. Under conditions in which the peaks are severely overlapped, the MDL may be only 1—2% wt. For elements with Z < 10, the MDL is usually around 1—2% wt. under the best conditions, especially in electron-beam instruments. 

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