Two spectra

Figure Bl.22.1. Reflection-absorption IR spectra (RAIRS) from palladium flat surfaces in the presence of a 1 X 10 Torr 1 1 NO CO mixture at 200 K. Data are shown here for tluee different surfaces, namely, for Pd (100) (bottom) and Pd(l 11) (middle) single crystals and for palladium particles (about 500 A m diameter) deposited on a 100 A diick Si02 film grown on top of a Mo(l 10) single crystal. These experiments illustrate how RAIRS titration experiments can be used for the identification of specific surface sites in supported catalysts. On Pd(lOO) CO and NO each adsorbs on twofold sites, as indicated by their stretching bands at about 1970 and 1670 cm, respectively. On Pd(l 11), on the other hand, the main IR peaks are seen around 1745 for NO (on-top adsorption) and about 1915 for CO (tlueefold coordination). Using those two spectra as references, the data from the supported Pd system can be analysed to obtain estimates of the relative fractions of (100) and (111) planes exposed in the metal particles [26].

The vibrations of acetylene provide an example of the so-called mutual exclusion mle. The mle states that, for a molecule with a centre of inversion, the fundamentals which are active in the Raman spectmm (g vibrations) are inactive in the infrared spectmm whereas those active in the infrared spectmm u vibrations) are inactive in the Raman spectmm that is, the two spectra are mutually exclusive. Flowever, there are some vibrations which are forbidden in both spectra, such as the torsional vibration of ethylene shown in Figure 6.23 in the >2 point group (Table A.32 in Appendix A) is the species of neither a translation nor a component of the polarizability. 

Pd4oCu4oP2o, Pd5oCu3oP2o, and Pd6oCu2oP20 alloys were measured by resonant ultrasound spectroscopy (RUS). In this technique, the spectrum of mechanical resonances for a parallelepiped sample is measured and compared with a theoretical spectrum calculated for a given set of elastic constants. The true set of elastic constants is calculated by a recursive regression method that matches the two spectra [28,29]. 

Figure 13.3 shows both the H and the l3C NMR spectra of methyl acetate, CH3CO2CH3. The horizontal axis shows the effective field strength felt by the nuclei, and the vertical axis indicates the intensity of absorption of rf energy. Each peak in the NMR spectrum corresponds to a chemically distinct 1H or 13C nucleus in the molecule. (Note that NMR spectra are formatted with the zero absorption line at the bottom, whereas IR spectra are formatted with the zero absorption line at the top Section 12.5.) Note also that 1H and 13C spectra can t be observed simultaneously on the same spectrometer because different amounts of energy are required to spin-flip the different kinds of nuclei. The two spectra must be recorded separately. 

Figure 60. Plot (top) of a regenerated spectrum (—) and the original spectrum (—) of a sample in training set Al together with (bottom) a separate plot of the differences between the two spectra.

At low rotation rates, less than the chemical shifts anisotropy, however, the powder spectra contained disturbing side bands dispersed among the isotropic chemical shifts. In order to discriminate between sidebands and isotropic resonances two spectra obtained at different spinning speeds were multiplied together or the differentiation was made by visual inspection. 

To examine the situation under simpler conditions, runs with xenon as sensitizer were made using low pressures of ethylene and NO. Two spectra are shown in Figure 16. The simplest spectrum is obtained with 25% NO. C4H8NO + and C2H5(NO)2+ dominate the spectrum. 

It is also possible to solubilize finite amounts of solid substances within reversed micelles [38 0], For example, in Figure 2, the UV-vis spectrum of CoCNOs) solubilized in reversed micelles of C12E4 is compared with that of a thin film of bulk Co(N03)2. It is interesting to note both similarities and differences between the two spectra. Another example is given by urea, which, as emphasized by the IR spectrum reported in Figure 3, can be... 

Figure 11. Quantum monodromy in the spectrum of the quadratic Hamiltonian of Eq. (38). The solid lines indicate relative equilibria. Filled circles mark the eigenvalues of the most stable isomer and those above the relevant effective potential barrier in Fig. 8. Open circles indicate interpenetrating eigenvalues of the secondary isomer. The transported unit cell moves over the hlled circle lattice, around the curved fold line connecting the two spectra.

An alternative combination pair of spectra is then formed, taking the geometric mean of two undulator spectra of positive helicity, and of the two recorded with negative helicity. These two spectra of given light helicity each contain corresponding corrected contributions from both undulator sources, and it can be shown [55] that the instrumental asymmetries are effectively canceled by this procedure. 

The fluorescence excitation spectrum of a Q-CdS sample, with several maxima in the absorption spectrum, also has a number of peaks. However, the maxima in the two spectra do not always occur at the same wavelengths This effect is not surprising, as excitation at different wavelengths leads to the excitation of particles of different sizes which do not have the me fluorescence intensity at the wavelength where the fluorescence is recorded. 

Fig. 10. Absorption spectra of aqueous solutions of [PtiNHalsClJCCIOJa and K4[Os(CN)6]. Left-hand curve separate solutions right-hand curve mixture. The broken curve gives the difference between the two spectra and corresponds to Os(IIFPt(IV) MMCT (after data in Ref. [62])...

It should be borne in mind that the two spectra given in Fig. 34.14 are estimates of the pure spectra, which exactly fulfil the constraints. Two other estimates of the pure spectra are the purest mixture spectra A and B. When plotted in the same figure (see Figs. 34.15 and 34.16) a good impression is obtained of the remaining... 

Fig. 5.4.7 (a-c, e) Spatially resolved NMR spectra detected during AMS hydrogenation in a catalyst bed of 1-mm beads. Each spectrum corresponds to a voxel size of 2 x 0.17 x 0.33 mm3. Spectra in (a-c) correspond to the same radial position within the operating reactor and are detected in the top, middle and bottom parts of the reactor, respectively. Three spectra in (b, e) correspond to the same vertical position in the operating reactor, with the two spectra in (e) corresponding to voxels shifted by 1.3 mm to ether side of the voxel of the spectrum in (b). The two spectra in (e) are shifted vertically relative to each other for better presentation. The lower traces with narrow lines in (d, f) are experimental spectra detected for bulk neat AMS (d) and cumene (f), the upper traces in (d, f) were obtained by mathematically broadening the lines to 300 Hz. 

Figure 8. The m/z 137 ion was selected from the source and colli-sionally decomposed (N ) to give the CAD spectra. The top spectrum is the fragment arising from the isolated xenognosin and the bottom two spectra arise from the isomeric benzyl alcohols ((3).

Preirradiation (selective 180°) of each signal was followed by a 90° observed pulse delayed by 0.7s. This spectrum (550-1000 transients) was acquired simultaneously with a spectrum in which one selective pulse was 3 ppm upfield of tetramethylsilane, and the two spectra were computer subtracted to observe the enhancements. 

Figure 2.5 illustrates two spectra recorded from a sample of iron using (a) Al Ka radiation, and (b) Mg Ko, radiation. The binding energy of the peaks are characteristic of each element. There is a difference in hv between these sources of 233 eV, so, as expected from equation (2.1), the XPS peaks on spectrum (a) are displaced 233 eV relative to those in spectrum (b). The spectrum was taken over a wide energy range to detect all possible peaks of elements present in the surface. The 2p and 3p peaks from iron are identified, as well as the Is peak from carbon which was present as a contaminant. 

Comparison of the two spectra confirms that there is an enrichment of Zn and Mg in the GP zone in the upper illustration. There is, however, no sign of Zn or Mg enrichment in the GP zone-like defect structure, as shown in the lower spectrum. 

The difference between these two spectra is shown in Figure 5.42(b). The shape of the difference spectrum depends on the magnitude of the scaling factor used to normalise the two spectra. These authors chose a factor so as to match the integrated intensities in a 50 eV window centred at 980 eV, 50 eV above the edge threshold. 

It is clear from the two spectra that resonances corresponding to inner carbohydrate residues, such as peaks 5, 6, and 13, display a much larger line-width than resonances corresponding to outer residues, such as peaks 2-4. This reflects the relative mobility of such residues, and aids in distinguishing between terminal residues and inner residues of the intact oligosaccharide chains of intact glycoproteins. 

Fig. 31 shows 220 MHz spectra for methyl cobalamin and methyl cobinamide. Most of the features of the PMR work to be discussed below can be illustrated with these two spectra as references. (See Fig. 1 for references to nomenclature.)... 

APT, you will perhaps remember, stands for Attached Proton Test, meaning that this spectrum tells you the multiphcity of the signals (Me, CH2, CH or quaternary C). These two spectra tell you how many magnetically non-equivalent types of carbon are present in the molecule, but (for the reasons we discussed earlier) we do not use integration to try to find out relative numbers. We shall present APT spectra as follows CH, CH3 in negative phase (down), CH2 and quaternary C in positive phase (up). 

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