3.3.3.105. NXxas_herfd

Status:

application definition (contribution), extends NXxas

Description:

High-energy resolution fluorescence detection (HERFD) is a particular ...

High-energy resolution fluorescence detection (HERFD) is a particular case of partial fluorescence yield measured with a crystal analyzer spectrometer with an energy bandwidth of approximately 1-2 eV.

The HERFD spectrum corresponds to a constant-emission-energy cut through the Resonant Inelastic X-ray Scattering (RIXS) plane. The spectral shape depends on the emission energy, making the emission line and emission energy mandatory metadata.

The top-level intensity field stores the ratio \(I_f/I_0\), where \(I_f\) is the fluorescence intensity diffracted by the crystal analyzer(s) and \(I_0\) is the incident beam intensity. This ratio is proportional to the absorption coefficient:

\[\mu(E) \propto I_f/I_0\]

The spectrometer uses Rowland circle geometry (Johann or Johansson type). Multiple crystal analyzers may be arranged at different horizontal angles around the sample to increase solid angle coverage.

When the raw detector data and processing steps are available, they can be stored in the optional NXinstrument, NXcollection, and NXprocess groups, enabling full reproducibility of the data reduction.

Symbols:

The symbol(s) listed here will be used below to coordinate datasets ...

The symbol(s) listed here will be used below to coordinate datasets with the same shape.

nEnergy: Number of energy data points

nAnalyzers: Number of crystal analyzers in the spectrometer

Groups cited:

NXbeam, NXcollection, NXcoordinate_system, NXcrystal, NXdetector, NXemission_line, NXentry, NXinstrument, NXnote, NXprocess, NXsample, NXsource, NXtransformations

Structure:

ENTRY: (required) NXentry ⤆

definition: (required) NX_CHAR ⤆

Official NeXus NXDL schema to which this file conforms. ...

Official NeXus NXDL schema to which this file conforms.

Obligatory value: NXxas_herfd

intensity: (required) NX_FLOAT (Rank: 1, Dimensions: [nEnergy]) {units=NX_ANY} ⤆

The ratio :math:`I_f/I_0`, where :math:`I_f` is the ...

The ratio \(I_f/I_0\), where \(I_f\) is the fluorescence intensity diffracted by the crystal analyzer(s) and \(I_0\) is the incident beam intensity.

emission_line: (required) NXemission_line

The emission line at which the HERFD spectrum is measured.

name: (required) NX_CHAR ⤆

emission_energy: (required) NX_FLOAT {units=NX_ENERGY}

The emission energy at which the spectrometer is set.

beamline_coordinate_system: (optional) NXcoordinate_system

Beamline coordinate system with the sample at the origin: ...

Beamline coordinate system with the sample at the origin: x along the beam, y horizontal, z opposite to gravity.

origin: (required) NX_CHAR ⤆

Obligatory value: sample

x_direction: (required) NX_CHAR ⤆

Obligatory value: along incident beam

y_direction: (required) NX_CHAR ⤆

Obligatory value: horizontal perpendicular to beam

z_direction: (required) NX_CHAR ⤆

Obligatory value: opposite to gravity

x: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Obligatory value: [1, 0, 0]

y: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Obligatory value: [0, 1, 0]

z: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Obligatory value: [0, 0, 1]

depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to transformations/beam.

transformations: (required) NXtransformations ⤆

Two rotations relating the beamline frame to ...

Two rotations relating the beamline frame to the NeXus laboratory frame, plus direction vectors labeling beam and gravity.

beam: (required) NX_NUMBER {units=NX_UNITLESS} ⤆

Direction of the incident beam in the beamline ...

Direction of the incident beam in the beamline coordinate system.

@vector: (required) NX_NUMBER ⤆

Obligatory value: [1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: gravity

gravity: (required) NX_NUMBER {units=NX_UNITLESS} ⤆

Direction of gravity in the beamline coordinate ...

Direction of gravity in the beamline coordinate system.

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, 0, -1]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: rotate_gravity_to_minus_y

rotate_gravity_to_minus_y: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Active rotation moving gravity from the ...

Active rotation moving gravity from the beamline direction (-z) to the NeXus direction (-y).

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: rotate_beam_to_plus_z

rotate_beam_to_plus_z: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Active rotation moving the beam from the ...

Active rotation moving the beam from the beamline direction (+x) to the NeXus direction (+z).

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, 1, 0]

@depends_on: (required) NX_CHAR ⤆

Should point to ``.`` (the NeXus laboratory ...

Should point to . (the NeXus laboratory frame).

SAMPLE: (required) NXsample ⤆

depends_on: (optional) NX_CHAR ⤆

The sample is at the origin of the beamline ...

The sample is at the origin of the beamline coordinate system, rotated about the vertical axis. Should point to transformations/sample_rotation.

transformations: (optional) NXtransformations ⤆

Orientation of the sample in the beamline ...

Orientation of the sample in the beamline coordinate system.

sample_rotation: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Rotation of the sample about the vertical axis, ...

Rotation of the sample about the vertical axis, orienting the sample surface between the incident beam and the crystal analyzers.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, 0, 1]

@depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to /entry/beamline_coordinate_system.

INSTRUMENT: (optional) NXinstrument ⤆

beam: (optional) NXbeam ⤆

The incident X-ray beam.

depends_on: (optional) NX_CHAR ⤆

Should point to ...

Should point to transformations/beam_direction.

transformations: (optional) NXtransformations ⤆

beam_direction: (required) NX_NUMBER {units=NX_UNITLESS} ⤆

Beam direction in the beamline coordinate ...

Beam direction in the beamline coordinate system. The beam travels along +x.

@vector: (required) NX_NUMBER ⤆

Obligatory value: [1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to /entry/beamline_coordinate_system.

SOURCE: (optional) NXsource ⤆

type: (required) NX_CHAR ⤆

name: (required) NX_CHAR ⤆

probe: (required) NX_CHAR ⤆

Obligatory value: x-ray

i0: (recommended) NXdetector ⤆

Detector measuring the incident beam intensity ...

Detector measuring the incident beam intensity \(I_0\), positioned upstream of the sample along the beam direction.

data: (required) NX_NUMBER (Rank: 1, Dimensions: [nEnergy]) ⤆

depends_on: (optional) NX_CHAR ⤆

Should point to ...

Should point to transformations/i0_distance.

transformations: (optional) NXtransformations ⤆

i0_distance: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Distance from the sample to the I0 detector, ...

Distance from the sample to the I0 detector, measured upstream along the beam (negative x direction in the beamline frame).

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: translation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [-1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to /entry/beamline_coordinate_system.

analyzerCRYSTAL: (required) NXcrystal ⤆

Crystal analyzer on the Rowland circle. For ...

Crystal analyzer on the Rowland circle. For multi-crystal spectrometers, use one group per crystal (e.g. analyzer1, analyzer2).

type: (optional) NX_CHAR ⤆

Type or material of the analyzer crystal ...

Type or material of the analyzer crystal (Si, Ge, etc.).

reflection: (optional) NX_INT (Rank: 1, Dimensions: [3]) {units=NX_UNITLESS} ⤆

Miller indices (hkl) values of the nominal ...

Miller indices (hkl) values of the nominal reflection.

d_spacing: (optional) NX_FLOAT {units=NX_LENGTH} ⤆

The spacing between crystal planes of the ...

The spacing between crystal planes of the reflection.

bragg_angle: (optional) NX_FLOAT {units=NX_ANGLE} ⤆

Bragg angle :math:`\theta_B` of the nominal ...

Bragg angle \(\theta_B\) of the nominal reflection.

bending_radius: (optional) NX_FLOAT {units=NX_LENGTH}

Bending radius of the spherically bent crystal ...

Bending radius of the spherically bent crystal analyzer. In Johann geometry this is \(2R_R\) (twice the Rowland radius).

rowland_radius: (optional) NX_FLOAT {units=NX_LENGTH}

Radius of the Rowland circle :math:`R_R`. The ...

Radius of the Rowland circle \(R_R\). The sample, crystal center, and detector focus all lie on this circle.

energy_resolution: (optional) NX_FLOAT {units=NX_ENERGY}

The energy bandwidth or resolution of the crystal ...

The energy bandwidth or resolution of the crystal analyzer.

geometry_type: (optional) NX_CHAR

The type of crystal analyzer geometry. ...

The type of crystal analyzer geometry.

Any of these values: Johann | Johansson

diameter: (optional) NX_FLOAT {units=NX_LENGTH}

Diameter of the crystal analyzer wafer.

depends_on: (optional) NX_CHAR ⤆

Should point to the last transformation in the ...

Should point to the last transformation in the chain, i.e. transformations/analyzer_distance.

transformations: (optional) NXtransformations ⤆

Transformation chain placing the analyzer relative ...

Transformation chain placing the analyzer relative to the sample: azimuthal angle, polar angle, then distance.

analyzer_distance: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Sample-to-analyzer distance.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: translation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: analyzer_polar_angle

analyzer_polar_angle: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Polar angle of the analyzer in the vertical ...

Polar angle of the analyzer in the vertical Rowland plane. Elevation from the horizontal beam plane to the sample-analyzer direction.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, -1, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: analyzer_azimuthal_angle

analyzer_azimuthal_angle: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Azimuthal (horizontal) angle of the ...

Azimuthal (horizontal) angle of the spectrometer arm from the incident beam direction. Rotation around the vertical z-axis. Typically around 90 degrees to minimize elastic scattering.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, 0, 1]

@depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to /entry/beamline_coordinate_system.

ifluor: (recommended) NXdetector ⤆

Detector measuring the fluorescence intensity ...

Detector measuring the fluorescence intensity \(I_f\) diffracted by the crystal analyzer(s).

data: (required) NX_NUMBER (Rank: 1, Dimensions: [nEnergy]) ⤆

depends_on: (optional) NX_CHAR ⤆

Should point to the last transformation in the ...

Should point to the last transformation in the chain, i.e. transformations/if_distance.

transformations: (optional) NXtransformations ⤆

Transformation chain placing the detector relative ...

Transformation chain placing the detector relative to the sample: azimuthal angle, polar angle, then distance.

if_distance: (required) NX_NUMBER {units=NX_LENGTH} ⤆

Distance from the sample to the detector.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: translation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [1, 0, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: if_polar_angle

if_polar_angle: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Polar angle of the detector in the vertical ...

Polar angle of the detector in the vertical Rowland plane.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, -1, 0]

@depends_on: (required) NX_CHAR ⤆

Obligatory value: if_azimuthal_angle

if_azimuthal_angle: (required) NX_NUMBER {units=NX_ANGLE} ⤆

Azimuthal (horizontal) angle of the detector ...

Azimuthal (horizontal) angle of the detector from the incident beam direction. Should match the analyzer azimuthal angle for on-Rowland focusing.

@transformation_type: (required) NX_CHAR ⤆

Obligatory value: rotation

@vector: (required) NX_NUMBER ⤆

Obligatory value: [0, 0, 1]

@depends_on: (required) NX_CHAR ⤆

Should point to ...

Should point to /entry/beamline_coordinate_system.

COLLECTION: (optional) NXcollection ⤆

Raw data as written by the acquisition software, ...

Raw data as written by the acquisition software, preserved without modification to allow independent reprocessing.

raw_data: (optional) NX_FLOAT (Rank: 2, Dimensions: [nEnergy, nAnalyzers])

Raw fluorescence counts per incident energy point for ...

Raw fluorescence counts per incident energy point for each crystal analyzer, before normalization by the incident beam intensity and summation over analyzers. Axis 0 is the energy scan axis; axis 1 enumerates the crystal analyzers, in the same order as the analyzerCRYSTAL groups.

PROCESS: (optional) NXprocess ⤆

Description of how :ref:`intensity ...

Description of how intensity was obtained from the raw detector data (i0, if).

program: (optional) NX_CHAR ⤆

Name of the program used for processing.

version: (optional) NX_CHAR ⤆

Version of the program used for processing.

date: (optional) NX_DATE_TIME ⤆

Date and time of processing.

note: (optional) NXnote ⤆

Python code reproducing the top-level :ref:`intensity ...

Python code reproducing the top-level intensity from the raw data.

type: (required) NX_CHAR ⤆

Mime content type of the note data field. ...

Mime content type of the note data field.

Obligatory value: text/x-python

data: (required) NX_CHAR

The Python code.

Hypertext Anchors

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

NXDL Source:

https://github.com/nexusformat/definitions/blob/main/contributed_definitions/NXxas_herfd.nxdl.xml