base class, extends NXobject


A wavelength defining device.

This is a base class for everything which selects a wavelength or energy, be it a monochromator crystal, a velocity selector, an undulator or whatever.

The expected units are:

  • wavelength: angstrom

  • energy: eV


No symbol table

Groups cited:

NXcrystal, NXdata, NXgeometry, NXgrating, NXoff_geometry, NXtransformations, NXvelocity_selector


@default: (optional) NX_CHAR

Declares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

wavelength: (optional) NX_FLOAT {units=NX_WAVELENGTH}

wavelength selected

wavelength_error: (optional) NX_FLOAT {units=NX_WAVELENGTH}

DEPRECATED: see https://github.com/nexusformat/definitions/issues/820

wavelength standard deviation

wavelength_errors: (optional) NX_FLOAT {units=NX_WAVELENGTH}

wavelength standard deviation

energy: (optional) NX_FLOAT {units=NX_ENERGY}

energy selected

energy_error: (optional) NX_FLOAT {units=NX_ENERGY}

DEPRECATED: see https://github.com/nexusformat/definitions/issues/820

energy standard deviation

energy_errors: (optional) NX_FLOAT {units=NX_ENERGY}

energy standard deviation

depends_on: (optional) NX_CHAR

NeXus positions components by applying a set of translations and rotations to apply to the component starting from 0, 0, 0. The order of these operations is critical and forms what NeXus calls a dependency chain. The depends_on field defines the path to the top most operation of the dependency chain or the string “.” if located in the origin. Usually these operations are stored in a NXtransformations group. But NeXus allows them to be stored anywhere.

distribution: (optional) NXdata

geometry: (optional) NXgeometry

DEPRECATED: Use the field depends_on and NXtransformations to position the monochromator and NXoff_geometry to describe its shape instead

OFF_GEOMETRY: (optional) NXoff_geometry

This group describes the shape of the beam line component

CRYSTAL: (optional) NXcrystal

Use as many crystals as necessary to describe

VELOCITY_SELECTOR: (optional) NXvelocity_selector

GRATING: (optional) NXgrating

For diffraction grating based monochromators

TRANSFORMATIONS: (optional) NXtransformations

This is the group recommended for holding the chain of translation and rotation operations necessary to position the component within the instrument. The dependency chain may however traverse similar groups in other component groups.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source: