Knowledge of the Orientals

For symmetric reflections the peak search may now begin. For asymmetric reflections, the specimen must be rotated about its normal until the desired diffraction vector lies in the incidence plane of the beam conditioner. This is normally the diffractometer surface. An accurate knowledge of the orientation of the specimen in two axes is required to set asymmetric reflections this is usually taken from the position of the orientation flat or groove. 

To do such syntheses it is essential to introduce the substituents in the proper order, which is based on the knowledge of the orientation and activation of both ring and incoming substituents. 

In such instances no knowledge of the orientation distribution or of / is required to compute 6V Once 6X is obtained, / can be calculated from equation (49), and using this / the 6 values for other moments can be obtained directly from the observed dichroic ratios. These relations demonstrate the potentialities of polarized radiation studies in providing structural information on high polymers. 

Detailed knowledge of the orientation of an adsorbed molecule is difficult to obtain by conventional surface scattering techniques such as LEED. The reason is that the electron is such a strongly interacting probe that multiple scattering effects... 

The molar magnetic susceptibility is usually related to the electronic structure of a transition metal complex through the well known Van Vleck equation41) which presupposes the knowledge of the orientation of the principal axes. For the molecules lacking the symmetry necessary to determine a priori these directions a more general expression was derived42) ... 

Polar alignment can be described physically through a knowledge of the orientational distribution function f ) (32). A related quantity that can be expressed as a single number is the order parameter. The order parameter describing the induced polar alignment G is given by... 

The van Vleck formula presupposes knowledge of the orientation of the principal molecular susceptibilities. For molecules lacking the symmetry a generalised expression has been derived [3]. 

The magnitudes and signs of D and E are defined with respect to the chosen coordinate system x,y,z (see Eq. (7.5a,b)). Without knowledge of the orientation of these coordinates relative to the system being investigated, the interpretation of D and E according to Eq. (7.5) permits no conclusions to be drawn about the orientation ofr. ... 

So far we have discussed the component of the angular momentum in the z direction, but no mention has been made of the components in the X and y directions. The reason for this omission is that the Uncertainty Principle forbids complete knowledge of the orientation of the angular momentum vector. If the component in the z direction is known, then the other two components must remain undetermined. This situation can be represented on a diagram by cones of uncertainty, as shown in Figure 5.11. One end of the angular momentum vector is... 

Factors (surface uniformity, splay, etc.) other than twist can limit contrast, hence an independent measurement of twist is important. It might be surmised that twist could be easily measured by determining the angular rotation of the plane of polarization of a beam passing through the cell. In practice, this is not possible without a knowledge of the orientation of the surface directors relative to the polars. 

The final connection between molecular properties and experimental observables requires knowledge of the orientational distribution of the emitting molecules with respect to the direction and polarization of the excitation light and the direction of detection, and the time dependence of this distribution. Substituting eq. (5) into eq. (6) we obtain the following general expression... 

The degree of molecular segmental orientation in a deformed amorphous polymeric network is obtained by the knowledge of the orientational distribution function. This distribution is represented by a function f(0 ),... 

This simple correlation, established first for these acids, was later shown to be valid also for cinnamides, stilbenes, fumarates, chalcones, coumarins, nucleotides, and other olefmic systems [10]. Indeed, it is possible to predict the stereochemistries of the photodimers from such materials, with a high degree of confidence, on the basis of knowledge of the orientations of the monomer molecules in the crystal. 

The interpretation of the polarization of fluorescence of labeled polymer chains requires a knowledge of the orientation of the transition moment of the label relative to the chain backbone (9). In copolymers of 9-p-vinylphenyl-10-phenylanthracene (10) these orientations are perpendicular to each other, while with the incorporation of an anthracene residue into the chain backbone (11) the transition moment of the label is parallel to the chain backbone ... 

Interpretation of the results requires a knowledge of the orientation of the water molecules on the platinum surface and the mechanism of infrared radiation absorption. 

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