(IUCr) CIF Definition save__diffrn_radiation.polarizn_source_norm

DRAFT DICTIONARY CBF/imgCIF Extensions Dictionary | Draft version 1.5 for comment

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Index

##### Image dictionary (imgCIF) version 1.5.4

# _diffrn_radiation.polarizn_source_norm

Name:
`'_diffrn_radiation.polarizn_source_norm'`

Definition:

            The angle in degrees, as viewed from the specimen, between
                   the normal to the polarization plane and the laboratory Y
                   axis as defined in the AXIS category.

                   Note that this is the angle of polarization of the source
                   photons, either directly from a synchrotron beamline or
                   from a monochromater.

                   This differs from the value of
                   _diffrn_radiation.polarisn_norm
                   in that _diffrn_radiation.polarisn_norm refers to
                   polarization relative to the diffraction plane rather than
                   to the laboratory axis system.

                   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 should be taken
                   as the XZ plane and the angle as 0.

                   See _diffrn_radiation.polarizn_source_ratio.

Type: float

Mandatory item: no

The permitted range is [-90.0, 90.0]
Enumeration default: 0.0

Category: diffrn_radiation

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Copyright © 2005 International Union of Crystallography