Deuterium scattered Intensity

Raman Spectroscopy. Raman spectroscopy is an excellent method for the analysis of deuterium containing mixtures, particularly for any of the diatomic H—D—T molecules. For these, it is possible to predict absolute light scattering intensities for the rotational Raman lines. Hence, absolute analyses are possible, at least in principle. The scattering intensities for the diatomic hydrogen isotope species is comparable to that of dinitrogen, N2, and thus easily observed. 

Figure 3. Angular distribution of the relative scattered intensity of deuterium molecules scattered from a) Ni(110) b) Ni(111). lite esqierlnental conditions were the same as in Figure 2.

Further H/D isotopic effects are (i) the increased intensities and decreased halfwidths of D2O (and HDO) bands compared to those of H2O in both the Raman and infrared spectra, and (ii) possible deviations from random distribution of H and D in partially deuterated specimens. From the relative intensities of the two OD (and OH) bands of HDO molecules in hydrates with strongly distorted water molecules (see Sect. 4.2.2) it is assumed that the hydrogen and deuterium atoms are not randomly distributed over the two H positions, but the deuterium atoms rather prefer those positions which are involved in stronger (weaker ) H-bonds. For theoretical studies of the i.r. absorption and Raman scattering intensities of free H2O, HDO, and D2O see Refs. 77,152. 

A special simplification arises when a deuterated polymer is blended with its hydrogenous counterpart of exactly the same molecular weight. In this case, the interference component of the scattered intensity turns out to be simply proportional to the independent scattering component, and as a result the form factor can be determined even when the concentration of the deuterated polymer is not dilute. This will be discussed more when the technique of deuterium labeling is described in Section 6.3. 

Table 6,1 Comparison of the Scattering Intensity for Hydrogen and Deuterium...

R(t) is the relevant function to be analyzed for extraction of the kinetics. However, in micellar systems where the micelles are not fully proteated/deuterated or there is residual contrast between core and shell, ncaiUnear interference scattering contributions are present. In order to take this into account, a more accurate description of the time-dependent scattering intensity is necessary. A scattering model, where the time-dependent hyrogen/deuterium composition of the core and shell of the micelles is built into a kinetic core-shell model, is described next. 

Fig. 8. Small-angle neutron scattered intensity plotted versus scattering vector q for salt-free deuterium oxide solutions of poly(2-vinyl pyridine), which possessed a molecular weight M = 281,000 g/mol prior to 45% methyl quaternization. Four different pol3mtier concentrations were examined 22 g/L (circles), 8.8 (squares), 4.5 g/L (upward triangles), and 2.2 g/L (downward triangles). Adapted from Ref 114.

The influence of the protein component of cytochrome c on the haem has also been investigated with the new technique of Raman difference spectroscopy. The basis of the method is similar to conventional difference spectroscopy and the resolution of the haem resonance has been increased S-fold. The method has also been used to study structural changes in methaemoglobin. Williams et a/. have used numerical methods to produce and interpret Raman difference spectra. These workers subtracted solvent spectra from protein spectra and showed that the amide I Raman scattering intensity could be used to define helix, sheet, and reverse turns with unparalleled accuracy. The method depends on computing reference spectra for each variety of secondary structure and fitting these in linear combination to the observed spectrum. The same technique has also been successfully applied to the amide III spectrum of proteins in deuterium oxide. ... 

Figure 1 shows the right-hand side of Eq. 1 versus (Q Rg) i where Rg is the root-mean-square radius of gyration of the triblock copolymer subunit, for a 10% deuterium-labeled triblock copolymer, and of both branched polymer 2 and branched polymer 3. The branched polymers in Fig. 1 are made up of the triblock copolymer also shown in Fig. 1. As it happens, all the gel approximations give virtually the same curve that is shown for branched polymer 3 in Fig. 1. The infinite branched polymers shown in Fig, 1 have a more pronounced maximum in their scattering intensity curves than their constituent triblock copolymer, but the position of the maximum with respect to Q is hardly shifted at all. Figure 2 shows the same comparisons as Fig. 1, but now the triblock copolymers are 50% deuterated. 

Since the SANS scattering intensity is generally described as depending, in part, on differences in the interaction energies sap of the hydrogenated and deuterated species, the random partial deuterium substitution leads to an additional interaction randomness that cannot presently be treated with the theory developed here. (The random partial deuteration presumably likewise affects the nuclear reaction analysis data.)... 

In the opposite sitnation, when the carbon is exposed to D O at RH=0.87 in association with a 1 1 (v/v) mixtnre of TH and TD (THD), a large difference is observed with respect to the case where the tolnene is fnlly deuterated (Fig. 6.4, curve 4). I. shows a substantial increase, to 0.11 cm , and the contrast factor also increases as a result of the replacement of deuterium atoms in the toluene (fep=H-0.66 X10 cm) by protons (b -0.37 x 10 cm). It is also noticeable that the accumulated intensity at the peak around 1.7 A is much weaker owing to the reduced scattering power of the TH molecules. 

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