Monochromatic specific intensities

We further address the influence of the pulse shape on the Sq S2 S process dynamics. For this purpose, simple pulse profiles are used in Ref. [42], shown in Figure 9.18, which can be modeled by analytical functions. More specifically, the profiles shown in the left panel of Figure 9.18 correspond to pulses composed from one, as pulse A, or three, as pulses B, C, and D, monochromatic pulses, as defined in Eqs (9.69) and (9.70). However, in all cases, the intensity and phase of each monochromatic pulse used in Eq. (9.69) is equal to 4TW/cm and zero, respectively. Moreover, the carrier frequencies of the monochromatic pulses are also the same in all cases, equal to 4.81 eV different carrier frequencies considered for profiles shown in the right part of Figure 9.18, are discussed below. The other parameters in Eqs. (9.69) and (9.70) regarding the pulses A, B, C, and D are as follows for pulse (A) with = 1, we have = 70 fs and = 24 fs for... 

Monochromatic detection. A schematic of a monochromatic absorbance detector is given in Fig. 3.12. It is composed of a mercury or deuterium light source, a monochromator used to isolate a narrow bandwidth (10 nm) or spectral line (i.e. 254 nm for Hg), a flow cell with a volume of a few pi (optical path 0.1 to 1 cm) and a means of optical detection. This system is an example of a selective detector the intensity of absorption depends on the analyte molar absorption coefficient (see Fig. 3.13). It is thus possible to calculate the concentration of the analytes by measuring directly the peak areas without taking into account the specific absorption coefficients. For compounds that do not possess a significant absorption spectrum, it is possible to perform derivatisation of the analytes prior to detection. 

OPTICAL EMISSION SPECTROCHEMICAL ANALYSIS. In this analytical technique, an optical device is used to analyze radiation from electrically excited sample atoms. The analyzing device provides monochromatic images whose intensities are measured and related to the concentration of the elements within the sample that produces the specific radiation measured. The technique is precise and rapid, and adaptable to solid, powder, or liquid samples. 

The second slit box is located on the detector arm between the sample and the detector. The slit nearest to the sample serves as a scatter slit. It is followed by another Soller slit and a receiving slit positioned just before the detector. The detector in this case is a solid-state detector, which is cooled by a built-in Peltier refrigerator enabling to adjust and maintain the detector sensitivity at extremely narrow width to allow only x-ray photons of specific energy to be registered. Monochromatization of the diffracted x-ray beam is, therefore, achieved electronically rather than by physical means (e.g. by a P-filter or a crystal monochromator), which increases the registered diffracted intensity by eliminating losses in the filter or in the monochromator. 

All monochromatization options discussed above have been used successfully in powder diffractometry. With point detectors, i.e. with those detectors, which register, diffracted intensity at a specific angle, one point at a time, either or both the incident and diffracted beam can be monochromatized. When position sensitive or image plate detectors are used, the only feasible option is to use a P-filter or a crystal monochromator to achieve monochromatization of the incident beam. As shown in Figure 3.16, for some materials the background becomes too high, which makes diffraction data nearly useless in the determination of the atomic parameters of the material. 

For some specific applications, they can be associated with traditional monochromators. An illustration of a typical configuration of this kind is shown in Figure 2.16a. A parabohc artificial crystal is irradiated by a divergent source, and the beam diffracted by this element is then diffracted by a monochromator comprised of two or four plane crystals [SCH 95]. The beam resulting from this system, sometimes referred to as a hybrid monochromator, is perfectly monochromatic and much more intense than in the absence of a parabolic artificial crystal. Note, however, that this beam is much wider than the initial beam produced by the source. Therefore, this monochromator is only used for particular types of configurations and these hybrid monochromators are essentially used for certain studies of epitaxial thin films [STO 97]. 

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