Transmission factor through crystal

As an X-ray beam passes through a crystal, its intensity is reduced as a result of its absorption by the material in the crystal. The extent of this intensity reduction " depends on the distance the diffracted beam must travel through the crystal, the nature of the atoms in the crystal, and the wavelength of the incident X-ray beam. It is described by the transmission factor (T, less than 1.0, also represented, causing great confusion, as A). The absorption correction [Abs or A, greater than 1.0) is the reciprocal of the transmission factor and is the amount by which the measured intensity should be artificially boosted in order... 

Alternatively, an experimental measurement can be made of the relative attenuation of a particular diffracted beam constantly set in the diffraction condition as the crystal is rotated, for example. In this case relative transmission factors can be calculated as a function of the angular setting. A different method of getting the absorption reference curve is to measure the transmission of the primary beam through the crystal this requires that the size of the primary beam is smaller than the smallest dimension of the crystal (Helliwell et al (1984b) and figure 6.3 (b)) Now for the reflection which is to be corrected, the angles of its primary and secondary beams are known. The relative transmission factors for the primary, Tp, and secondary, Ts, beams can be determined... 

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