.. include:: /substitutions.txt

.. _api.reflection:

======================
Orientation Reflection
======================

An orientation :index:`reflection` is a peak intensity (typically an
observation) due to diffraction from a specific orientation of a crystalline
sample with respect to the incident radiation. The reflection occurs for a
precise alignment of the sample's crystalline planes and diffractometer axes
with the incoming radiation. 

The coordinates of two (or more) reflections are used to compute a sample's
:math:`UB` :index:`orientation matrix`.  :math:`UB` transforms between the
sample's crystallographic axes (:index:`reciprocal-space`) and the
diffractometer's physical axes (:index:`real-space`).

Each reflection is defined by:

* full set of diffractometer angles - *real axes*
* reciprocal-space coordinates - *pseudo axes*
* wavelength of the incident radiation

Note that the engineering units for the pseudo axes are the reciprocal of the
units of the wavelength (where *angstroms* is typical).  The angles are reported
in *degrees*.

Source Code Documentation
-------------------------

.. automodule:: hklpy2.operations.reflection
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