Spectra can be calculated either for powders or oriented samples. While in a powder all orientations are contributing to the spectrum with equal weight, oriented samples are characterized by a preferred direction and an orientational distribution function, which has to be taken into account when summing up all contributions. 
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Weblab is restricted to oriented samples with an uni-axial orientation. 
In this case the orientation of the mesogenic units with respect to the preferred direction, the director, can be described by a distribution function, which depends on the angle &beta;<sub>D</sub> between the director and the z-axes of these units only.
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The pictures below show the coordinate systems involved. The <i>mesogenic frame</i> ist attached to the mesogenic unit. Its z-axis z<sub>G</sub> has an angle &beta;<sub>D</sub> with the director, which is assumed to be distributed according to the chosen distribution function (see topic &DoubleRightArrow; <a href="javascript:help('orderangle','Order and Field Angle')">Order and Field Angle</a>). The solid state spectrum is fianlly obtaind by integrating over the set of Euler angles &alpha;<sub>L</sub>,&beta;<sub>L</sub> und &gamma;<sub>L</sub>.  
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<center>
<img src="help/images/frames-order.png" alt="Coordinate Systems Orientiation">
<img src="help/images/orient.png" alt="Orientation Model" width=60%></center>
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Weblab can consider orientional order also in the intermediate motional regime. A treatment of order together with MAS is not supported.