3.3.3.104. NXxas

Status:

application definition (contribution), extends NXobject

Description:

This is a generic application definition for X-ray absorption ...

This is a generic application definition for X-ray absorption spectroscopy. Technique-specific application definitions extend this base definition.

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.

nP: Number of stacked spectra (scan points). This is the growable first dimension: data could be appended along it during acquisition. It is absent when a single spectrum is stored.

nEnergy: Number of energy data points

dataRank: Rank of the intensity field: 1 for a single spectrum [nEnergy] or 2 for a stack of spectra [nP, nEnergy].

Groups cited:

NXabsorption_edge, NXdata, NXelement, NXentry, NXsample

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

element: (required) NXelement

The element being probed by the incident X-rays.

name: (required) NX_CHAR

edge: (required) NXabsorption_edge

The absorption edge being probed, defined by the principal ...

The absorption edge being probed, defined by the principal quantum number and orbital symmetry of the photoionized electron (e.g. K, L1, L2, L3, L2,3). Together with the element uniquely identifies probed electronic transition.

is_experimental: (required) NX_BOOLEAN

Specify if the data comes from an experiment. Use ``true`` for ...

Specify if the data comes from an experiment. Use true for data acquired at a beamline or laboratory instrument, and false for spectra calculated/simulated using a computational tool, reconstructed from a linear combination of reference components, etc.

energy: (required) NX_FLOAT (Rank: 1, Dimensions: [nEnergy]) {units=NX_ENERGY}

The energy axis of the spectrum.

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

The intensity of the spectrum. The precise definition of what is ...

The intensity of the spectrum. The precise definition of what is meant by intensity depends on the acquisition mode, and will be specified by each subclass application definition.

intensity_errors: (optional) NX_FLOAT (Rank: dataRank, Dimensions: [nP, nEnergy]) {units=NX_ANY}

The errors associated with the intensity of the spectrum.

SAMPLE: (required) NXsample ⤆

name: (required) NX_CHAR ⤆

Descriptive name of the sample

temperature: (optional) NX_FLOAT (Rank: 1, Dimensions: [nP]) {units=NX_TEMPERATURE} ⤆

Sample temperature.

DATA: (optional) NXdata ⤆

Plot of the X-ray absorption intensity versus energy. ...

Plot of the X-ray absorption intensity versus energy.

When several spectra are stacked along nP (a time series, a spatial map, an operando series, …), the quantity that varies across the stack is stored in its standard NeXus location (for example NXsample/temperature, NXsample/electric_field, an NXsample/NXtransformations axis, or an NXbeam polarization field) and linked here as an additional axis with its AXISNAME_indices set to 0, the nP dimension. The application definition does not enumerate these coordinates: any of them, including ones not listed here, is declared simply by adding the field in its base-class location and wiring it into this group.

energy: (required) NX_CHAR

intensity: (required) NX_CHAR

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.nxdl.xml