Indicates the method used to obtain monochromatic radiation.
_diffrn_radiation.monochromator describes the primary beam
monochromator (pre-specimen monochromation).
_diffrn_radiation.pdbx_analyzer specifies the
post-diffraction analyser (post-specimen) monochromation.
Note that monochromators may have either 'parallel' or
'antiparallel' orientation. It is assumed that the
geometry is parallel unless specified otherwise.
In a parallel geometry, the position of the monochromator
allows the incident beam and the final post-specimen
and post-monochromator beam to be as close to parallel
as possible. In a parallel geometry, the diffracting
planes in the specimen and monochromator will be parallel
when 2*theta(monochromator) is equal to 2*theta (specimen).
For further discussion see R. Jenkins and R. Snyder,
Introduction to X-ray Powder Diffraction, Wiley (1996),