.. NeXus - Neutron and X-ray Common Data Format Copyright (C) 2009-2026 NeXus International Advisory Committee (NIAC) This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA For further information, see http://www.nexusformat.org Unit categories in NXDL specifications describe the expected type of units for a NeXus field. They should describe valid units consistent with the manual section on NeXus units (based on UDUNITS). Units are not validated by NeXus. units of angle rad units for things like logs that aren't picky on units units of area m^2 barns units of quantity of item(s) such as number of photons, neutrons, pulses, or other counting events units of area (alias of NX_AREA) barn units of electrical charge C units of electrical current A units for fields where the units cancel out (NOTE: not the same as NX_UNITLESS) m/m units of emittance (``length * angle``) of a radiation source nm*rad units of energy J keV units of flux 1/s/cm^2 units of frequency Hz units of length m units of mass g units of mass density g/cm^3 units of molecular weight g/mol units of 1/length^2 1/m^2 units of 1/length 1/m units of time, period of pulsed source (alias to `NX_TIME`) us units of power W units of pressure Pa DEPRECATED: see NX_COUNT units of clock pulses (alias to `NX_NUMBER`) units of scattering length density m/m^3 units of solid angle sr steradian units of temperature K units of time s units of (neutron) time of flight (alias to `NX_TIME`) s units of the specified transformation could be any of these: ``NX_LENGTH``, ``NX_ANGLE``, or ``NX_UNITLESS`` There will be one or more transformations defined by one or more fields for each transformation. The units type ``NX_TRANSFORMATION`` designates the particular axis generating a transformation (e.g. a rotation axis or a translation axis or a general axis). ``NX_TRANSFORMATION`` designates the units will be appropriate to the type of transformation, indicated in the :ref:`NXtransformations` base class by the ``transformation_type`` value: * ``NX_LENGTH`` for ``translation`` * ``NX_ANGLE`` for ``rotation`` * ``NX_UNITLESS`` for axes for which no transformation type is specified. for fields that don't have a unit (e.g. hkl) so that they don't inherit the wrong units (NOTE: not the same as NX_DIMENSIONLESS) "" units of voltage V units of volume m^3 units of wavelength angstrom units of wavenumber or Q 1/nm 1/angstrom any valid NeXus field or attribute type A string of characters. The preferred string encoding is :index:`UTF-8`. This is the default field type. any representation of a floating point number any representation of an integer number any representation of an unsigned integer number (includes zero) any representation of a positive integer number (greater than zero) any valid NeXus number representation Compound type cartesian representation of complex numbers (real and imaginary parts) in NeXus. Compound type polar representation of complex numbers (amplitude and phase *in radians*) in NeXus. Compound type representation of complex numbers (either cartesian or polar form) in NeXus. Compound type representation of quaternion numbers (real,i,j,k) in NeXus. Alias for the ``ISO8601`` date/time stamp. It is recommended to add an explicit time zone, otherwise the local time zone is assumed per ISO8601. ISO8601 date/time stamp. It is recommended to add an explicit time zone, otherwise the local time zone *is assumed* per ISO8601. The norm is that if there is no time zone, it is assumed local time, however, when a file moves from one country to another it is undefined. If the local time zone is written, the ambiguity is gone. true/false value ( true | 1 | false | 0 ) any representation of binary data - if text, line terminator is [CR][LF] Any valid character string or NeXus number representation