Orientation-dependent line-intensity ratio

The relative intensities of the lines in a Mossbauer spectrum provide additional information about the orientation of the hyperfine fields with respect to the crystal system in the case of single crystals or partially oriented (textured) samples. For pure magnetic or electric hyperfine fields the intensities are analytical expressions dependent on the direction of the fields with respect to the direction of y-radiation. For powder samples the intensity ratios of pure transitions do not depend on the strength of the fields. 

Chemical identification of unknowns by XRD relies in the accurate determination of a set of ii-spacings for the various crystallographic orientations. The data are screened against database of reference materials which are typically powder data with no preferred orientation. Accuracy of XRD identification of unknown species depends on the careful preparation of the samples, if powder form is required. On the other hand, if samples are not in powder form, care must be taken to account for missing lines in the XRD pattern and for abnormal intensity ratio in the observed peaks due to preferred orientation (texture). Detection limits in this case are within 0.1-1 wt%, which is worse than the ppm or ppb levels provided by surface analysis methods such as XPS or SIMS (discussed in this book). Chemical determination by XRD is limited to crystalline phases rally, but compounds can be identified down to their polymorphic phases. 

Fig. 29 Upper panels. Neutron scattering intensities obtained from a CPCl/Hex nematic micellar solution in the (qv,qvv)-plane at different shear rates (a) j =0.94 s , (b) y=34.5 s ,and (c) 7= 250 s . The nematic phase was made in deuterated water at concentration c = 35.2wt.% and molar ratio [Hex]/[CPC1] = 0.49 [301], Lower panel. Shear rate dependence of the orientational order parameter y (Eq. 5) obtained from the SANS cross-sections shown in the upper panel. The continuous line is a guide for the eyes. The increase of the order parameter was interpreted in terms of a transition between the tumbling and the flow-alignment regimes [290,303]...

Despite random orientation of the molecule with respect to the direction of the laser beam polarization, the intensity of a Raman line for substances in the gaseous and liquid phase depends on the polarization of the incident beam and the symmetry of the vibrational mode. For geometries of Raman experiments as illustrated in Figure 17, the ratio of the X-polarized (IJ to the Z-polarized (In) Raman intensity at any frequency is, by definition, the depolarization ratio p ... 

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