Wavelength dispersive spectroscopy

In WDS, the analyzing crystal should be carefully selected because it determines the range of detectable atomic numbers. The wavelength that can be detected by a crystal is defined by Bragg s Law. 

Normally, the maximum achievable 9 angle in a WDS system is about 73°. Thus, the maximum X of characteristic X-rays being diffracted is about 1.9d of the analyzing crystal. Table 6.4 lists the commonly used analyzing crystals for WDS, which include LiF, pentaerythrital (PE), thallium acid phthalate (TAP) and layered synthetic microstructure (LSM). For detecting light 

Crystal Plane Plane spacing, 2d (A) Atomic number range 

Equation 6.3 implies that we will obtain the wave spectrum of higher resolution when using a small ( /-spacing crystal. However, using the analyzing crystal with a small d will reduce the range of wavelength to be detected because of the 1.9d limit. 

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The incoming electron beam interacts with the sample to produce a number of signals that are subsequently detectable and useful for analysis. They are X-ray emission, which can be detected either by Energy Dispersive Spectroscopy, EDS, or by Wavelength Dispersive Spectroscopy, WDS visible or UV emission, which is known as Cathodoluminescence, CL and Auger Electron Emission, which is the basis of Auger Electron Spectroscopy discussed in Chapter 5. Finally, the incoming... 

X-Ray Fluorescence analysis (XRF) is a well-established instrumental technique for quantitative analysis of the composition of solids. It is basically a bulk evaluation method, its analytical depth being determined by the penetration depth of the impinging X-ray radiation and the escape depth of the characteristic fluorescence quanta. Sensitivities in the ppma range are obtained, and the analysis of the emitted radiation is mosdy performed using crystal spectrometers, i.e., by wavelength-dispersive spectroscopy. XRF is applied to a wide range of materials, among them metals, alloys, minerals, and ceramics. 

This EPMA line scan was analysed by wavelength dispersive spectroscopy, being part of a study by Horz and Kallfass of ornamental and ceremonial artifacts dated to approximately AD 50-300, recovered from the Royal Tombs of Sipan, Peru. 

This chapter summarizes results obtained during the past 5 years, on the design, preparation and study of titanium and vanadium compounds as candidate precursors to TiC, TiN, VC, and VN. The study of the precursor molecules was conducted through several steps. After their synthesis, thermoanalytical studies (TG-DTA), coupled to simultaneous mass spectroscopic (MS) analysis of the decomposition gases, were carried out to determine their suitability as precursors. CVD experiments were then conducted and were followed by characterization of the deposits by scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microprobe analysis with wavelength dispersion spectroscopy (EPMA-WDS). 

The thickness of the deposits was determined by the ball cratering method or SEM measurement of cross-sections. The elemental composition was determined by electron microprobe analysis with wavelength dispersive spectroscopy (EPMA-WDS) on a Camebax Cameca equipment and by X-ray photoelectron spectroscopy (XPS) on a VG Escalab MK2 apparatus... 

Bulk spectroscopic techniques such as x-ray fluorescence and optical and infrared spectroscopies involve minimal sample preparation beyond cutting and mounting the sample. These are discussed in Section 9.2.1. Spectroscopic techniques such as wavelength dispersive spectroscopy (WDS) and energy dispersive spectroscopy (EDS) are performed inside the SEM and TEM during microscopic analysis. Therefore, the sample preparation concerns there are identical to those for SEM and TEM sample preparation as covered in Section 9.3. Some special requirements are to be met for surface spectroscopic techniques because of the vulnerability of this region. These are outlined in Section 9.5. 

Figure 9.9 Thin-section micrograph (PPL) of a pore in the 72-80-cm depth horizon from Bagnoli soil completely covered by dark clay coatings and potentially toxic metals (PTMs j quantification (mg kg ) in the coatings as determined by the wavelength dispersive spectroscopy (WDS) (average of 40 points around the pore) (from Adamo et al., 2002a).

The toxicity of the mineral is such that quantitative characterization of erionite is extremely important. Samples should be characterized by using one or more of the following techniques (1) powder X-ray diffraction, (2) electron probe microanalysis or inductively coupled plasma-mass spectroscopy, (3) scanning electron microscopy equipped with wavelength dispersive spectroscopy (WDS) and/or energy dispersive spectroscopy (EDS), (4) transmission electron microscopy equipped with WDS and/or EDS and selected area electron diffraction, and (5) similar or better analytical techniques. 

Wall sections of the monolithic support whith the best catalytic performance was analysed by Electron Probe Microanalysis by Wavelength Dispersion Spectroscopy... 

Spectroscopy and spectrometry [using X-rays for energy dispersive spectrometry (EDS) and wavelength dispersive spectroscopy (WDS), Raman, infrared (IR), etc.]... 

The electron microprobe or WDS can provide accurate chemical analysis or a chemical profile across the interface. The wavelength of the X-rays emitted when the electron beam interacts with the sample is measured. Wavelength dispersive spectroscopy is more accurate than XEDS, but is a serial acquisition, so it is slower. Table 10.10 compares WDS and XEDS. 

The scientist s way is to use X-ray diffraction (XRD), X-ray energy-dispersive spectrometry (XEDS), wavelength-dispersive spectroscopy (WDS), or comparable techniques for chemical analysis. 

Ferl] Wavelength dispersive spectroscopy, resistivity measurements Partial isothermal section at 1050°C, (Cu)-phase... 

The chemical composition of the natural beryl sample used in this study was analyzed by X-ray wavelength dispersive spectroscopy for major atomic contents, inductivity coupled plasma-atomic emission spectroscopy for Be content, and atomic absorption sp>ectroscopy for Li and Rb contents (Table 1). The type I/II H2O contents were determined from intensities of IR bands due to the asymmetric stretching of type I and the symmetric stretching of type II in a polarized IR spectrum at RT (See the spectrum in the next section), using their molar absorption coefficients of 206 L moH cm-i and 256 L moH cm-i. 

Mun] Thermal analysis of levitated specimens by two-color optical pyrometer, XRD, energy dispersive spectroscopy, wavelength dispersive spectroscopy, optical microscopy 5 to 96 at.% Cu, 2 to 80 at.% Co, 2 to 85 at.% Fe, melting temperatures, melt separation temperatures... 

SEM is probably the optimal method for characterizing the particle morphology— shape, size, and porosity. With the addition of energy-dispersive spectroscopy (EDS) or wavelength-dispersive spectroscopy (WDS), the elemental composition of the particle can also be obtained in the SEM. The whole stub can be transferred to a SIMS chamber or LA-ICPMS cell and the coordinates of the particles, obtained from the SEM, can be used for direct measurement of the isotopic composition or, as mentioned earlier, individual particles can be manipulated and transferred. 

In XRF, the polychromatic beam of radiation emitted from the specimen is diffracted through a single crystal to isolate narrow wavelength bands (wavelength dispersive spectroscopy) or analyzed with a proportional detector to isolate narrow energy bands (energy dispersive spectroscopy). Because the relationship between... 

Energy dispersive x-ray spectroscopy can be conducted in the SEM STEM and AEM whereas wavelength dispersive spectroscopy is conducted only in the SEM or EPMA. For light element analysis, from boron to sodium, the WDS technique is preferred to ultrathin window EDS for polymers, so the AEM should not be used. 

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