Porto notation

Maximum information is obtained by making Raman measurements on oriented, transparent single crystals. The essentials of the experiment are sketched in Figure 3. The crystal is aligned with the crystallographic axes parallel to a laboratory coordinate system defined by the directions of the laser beam and the scattered beam. A useful shorthand for describing the orientational relations (the Porto notation) is illustrated in Figure 3 as z(xz) y. The first symbol is the direction of the laser beam the second symbol is the polarization direction of the laser beam the third symbol is the polarization direction of the scattered beam and the fourth symbol is the direction of the scattered beam, all with respect to the laboratory coordinate system. 

Zircon belongs to the tetragonal system and is a positive uniaxial. The typical form shows the ill and the 110 planes. The two orientations selected for luminescence polarization study were the (110) plane, parallel to the basal section and the [100] row. In such cases the axis perpendicular to the (110) plane will be called X. The orientation notation is made according to the so-called Porto notation (Porto et al. 1956). The Xi(ZX2)Xi orientation means that the laser light entered parallel to the Xi axis of the crystal and is polarized in the Z direction, while the emission is collected along the Xi axis with X2 polarization. By polarization spectroscopy with a high spectral resolution (less then 0.1 nm) six lines are observed for the Dq- Fi transition of the Eu-II center instead of the maximum three allowed for an unique site (Fig. 5.12). In Z(XX)Z geometry which corresponds to observation of a-polarized luminescence we... 

Table 5 Possible Experimental Geometrical Arrangements and the Corresponding Porto Notation for the Detection of Modes Belonging to the 6Big (R xy) Irreducible Representations of the Dsft Group of, for example, PbCb...

Figure 28 shows the evolution with several phase transformations in lithium formate monohydrate (FLMH) LiHC00 H20 as T is increased from 313 to 491 K. Note the two different Porto notations indicating the polarization configurations which allow detection of the mentioned Bi and Ai modes [48]. 

Figure 3-7. Raman spectra in polarized light of stretch-oriented high density polyethylene. Experiments were taken in different scattering geometries. Porto s notation is used in the definition of the scattering geometries. Space group symmetry species are indicated (from f63]i.

A convenient notation for describing polarization data from single crystals is due to S. Porto. This involves four symbols (usually chosen from x, y, z axis designations), which define the propagation direction of the incident radiation, the direction of the E of the incident radiation, the direction of the E of the scattered radiation being examined, and the direction of propagation of the scattered radiation. The second and third symbols are placed in parentheses, for example, z(xy)x, and define the components of the scattering tensor. 

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