Index

Image CIF dictionary (imgCIF) version 3.00.04

_diffrn_radiation.polarizn_source_ratio

Definition:

   
     (Ip-In)/(Ip+In), where Ip is the intensity
     (amplitude squared) of the electric vector in the plane of
     polarization and In is the intensity (amplitude squared)
     of the electric vector in the plane of the normal to the
     plane of polarization.
     In the case of an unpolarized beam, or a beam with true
     circular polarization, in which no single plane of
     polarization can be determined, the plane is to be taken
     as the XZ plane and the normal is parallel to the Y axis.
     Thus, if there was complete polarization in the plane of
     polarization, the value of
     _diffrn_radiation.polarizn_source_ratio would be 1, and
     for an unpolarized beam
     _diffrn_radiation.polarizn_source_ratio would have a
     value of 0.
     If the X axis has been chosen to lie in the plane of
     polarization, this definition will agree with the definition
     of 'MONOCHROMATOR' in the Denzo glossary, and values of near
     1 should be expected for a bending-magnet source.  However,
     if the X axis were perpendicular to the polarization plane
     (not a common choice), then the Denzo value would be the
     negative of _diffrn_radiation.polarizn_source_ratio.
     See http://www.hkl-xray.com for information on Denzo and
     Otwinowski & Minor (1997).
     This differs both in the choice of ratio and choice of
     orientation from _diffrn_radiation.polarisn_ratio, which,
     unlike _diffrn_radiation.polarizn_source_ratio, is
     unbounded.
     Reference: Otwinowski, Z. & Minor, W. (1997). 'Processing of
     X-ray diffraction data collected in oscillation mode.' Methods
     Enzymol. 276, 307-326.

Type: Real

Category:
diffrn_radiation