2.3.3.3.109. NXelectronanalyser

Status:

base class, extends NXobject

Description:

Basic class for describing a electron analyzer. ...

Basic class for describing a electron analyzer.

This concept is related to term 12.59 of the ISO 18115-1:2023 standard.

Symbols:

The symbols used in the schema to specify e.g. dimensions of arrays

nfa: Number of fast axes (axes acquired simultaneously, without scanning a physical quantity)

nsa: Number of slow axes (axes acquired scanning a physical quantity)

n_transmission_function: Number of data points in the transmission function.

Groups cited:

NXcollectioncolumn, NXdata, NXdeflector, NXdetector, NXenergydispersion, NXfabrication, NXlens_em, NXresolution, NXspindispersion, NXtransformations

Structure:

@default: (optional) NX_CHAR

Declares which child group contains a path leading ...

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.

description: (optional) NX_CHAR

Free text description of the type of the detector

name: (optional) NX_CHAR

Name or model of the equipment

@short_name: (optional) NX_CHAR

Acronym or other shorthand name

work_function: (optional) NX_FLOAT {units=NX_ENERGY}

Work function of the electron analyser. ...

Work function of the electron analyser.

The work function of a uniform surface of a conductor is the minimum energy required to remove an electron from the interior of the solid to a vacuum level immediately outside the solid surface.

The kinetic energy \(E_K\) of a photoelectron emitted from an energy-level with binding energy \(E_B\) below the Fermi level is given by \(E_K = h\nu - E_B - W = h\nu - E_B - e \phi_{\mathrm{sample}}\). Here, \(W = e \phi_{\mathrm{sample}}\) is the work function of the sample surface (with the potential difference \(\phi_{\mathrm{sample}}\) between the electrochemical potential of electrons in the bulk and the electrostatic potential of an electron in the vacuum just outside the surface).

In PES measurements, the sample and the spectrometer (with work function \(\phi_{\mathrm{spectr.}}\)) are electrically connected and therefore their Fermi levels are aligned. Due to the difference in local vacuum level between the sample and spectrometer, there exists an electric potential difference (contact potential) \(\Delta\phi = \phi_{\mathrm{sample}} - \phi_{\mathrm{spectr.}}\). The measured kinetic energy of a photoelectron in PES is therefore given by \(E_K^{\mathrm{meas.}} = h\nu - E_B + \Delta \phi = h\nu - E_B - e \phi_{\mathrm{spectr.}}\). As a result, the measured kinetic energy \(E_K^{\mathrm{meas.}}\) of a photoelectron is independent of the sample work function. Nonetheless, the work function \(\phi_s\) needs to be known to accurately determine the binding energy scale.

voltage_energy_range: (optional) NX_FLOAT {units=NX_VOLTAGE}

Energy range of the voltage supplies. This influences the noise of the supplie ...

Energy range of the voltage supplies. This influences the noise of the supplies, and thereby the energy resolution.

fast_axes: (optional) NX_CHAR (Rank: 1, Dimensions: [nfa])

List of the axes that are acquired simultaneously by the detector. ...

List of the axes that are acquired simultaneously by the detector. These refer only to the experimental variables recorded by the electron analyser. Other variables such as temperature, manipulator angles etc. are labeled as fast or slow in the data.

Examples

Mode

fast_axes

slow_axes

Hemispherical in ARPES mode

[‘energy’, ‘kx’]

Hemispherical with channeltron, sweeping energy mode

["energy"]

Tof

[‘energy’, ‘kx’, ‘ky’]

Momentum microscope, spin-resolved

[‘energy’, ‘kx’, ‘ky’]

[‘spin up-down’, ‘spin left-right’]

Axes may be less abstract than this, i.e. [‘detector_x’, ‘detector_y’]. If energy_scan_mode=sweep, fast_axes: [‘energy’, ‘kx’]; slow_axes: [‘energy’] is allowed.

slow_axes: (optional) NX_CHAR (Rank: 1, Dimensions: [nsa])

List of the axes that are acquired by scanning a physical parameter, listed in ...

List of the axes that are acquired by scanning a physical parameter, listed in order of decreasing speed. See fast_axes for examples.

depends_on: (optional) NX_CHAR

Refers to the last transformation specifying the position of the electron anal ...

Refers to the last transformation specifying the position of the electron analyser in the NXtransformations chain.

energy_resolution: (optional) NXresolution

Energy resolution of the analyser with the current setting. May be linked from ...

Energy resolution of the analyser with the current setting. May be linked from an NXcalibration.

physical_quantity: (optional) NX_CHAR ⤆

Obligatory value: energy

resolution: (optional) NX_FLOAT {units=NX_ENERGY} ⤆

Minimum distinguishable energy separation in the energy spectra. ...

Minimum distinguishable energy separation in the energy spectra.

This concept is related to term 10.24 of the ISO 18115-1:2023 standard.

resolution_errors: (optional) NX_FLOAT {units=NX_ENERGY} ⤆

relative_resolution: (optional) NX_FLOAT ⤆

Ratio of the energy resolution of the electron analyser at a specified energ ...

Ratio of the energy resolution of the electron analyser at a specified energy value to that energy value.

This concept is related to term 10.7 of the ISO 18115-1:2023 standard.

momentum_resolution: (optional) NXresolution

Momentum resolution of the electron analyser (FWHM)

physical_quantity: (optional) NX_CHAR ⤆

Obligatory value: momentum

resolution: (optional) NX_FLOAT {units=NX_WAVENUMBER} ⤆

resolution_errors: (optional) NX_FLOAT {units=NX_WAVENUMBER} ⤆

angular_resolution: (optional) NXresolution

Angular resolution of the electron analyser (FWHM)

physical_quantity: (optional) NX_CHAR ⤆

Obligatory value: angle

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

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

spatial_resolution: (optional) NXresolution

Spatial resolution of the electron analyser (Airy disk radius) ...

Spatial resolution of the electron analyser (Airy disk radius)

This concept is related to term 10.14 of the ISO 18115-1:2023 standard.

physical_quantity: (optional) NX_CHAR ⤆

Obligatory value: length

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

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

transmission_function: (optional) NXdata

Transmission function of the electron analyser. ...

Transmission function of the electron analyser.

The transmission function (TF) specifies the detection efficiency per solid angle for electrons of different kinetic energy passing through the electron analyser. It depends on the spectrometer geometry as well as operation settings such as lens mode and pass energy. The transmission function is usually given as relative intensity vs. kinetic energy.

The TF is used for calibration of the intensity scale in quantitative XPS. Without proper transmission correction, a comparison of results measured from the same sample using different operating modes for an instrument would show significant variations in atomic concentrations.

This concept is related to term 7.15 of the ISO 18115-1:2023 standard.

@signal: (optional) NX_CHAR ⤆

Obligatory value: relative_intensity

@axes: (optional) NX_CHAR ⤆

Obligatory value: kinetic_energy

kinetic_energy: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_transmission_function]) {units=NX_ENERGY}

Kinetic energy values

relative_intensity: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_transmission_function]) {units=NX_UNITLESS}

Relative transmission efficiency for the given kinetic energies

TRANSFORMATIONS: (optional) NXtransformations

Collection of axis-based translations and rotations to describe the location a ...

Collection of axis-based translations and rotations to describe the location and geometry of the electron analyser as a component in the instrument. Conventions from the NXtransformations base class are used. In principle, the McStas coordinate system is used. The first transformation has to point either to another component of the system or “.” (for pointing to the reference frame) to relate it relative to the experimental setup. Typically, the components of a system should all be related relative to each other and only one component should relate to the reference coordinate system.

COLLECTIONCOLUMN: (optional) NXcollectioncolumn

Describes the electron collection (spatial and momentum imaging) column

ENERGYDISPERSION: (optional) NXenergydispersion

Describes the energy dispersion section

SPINDISPERSION: (optional) NXspindispersion

Describes the spin dispersion section

DETECTOR: (optional) NXdetector

Describes the electron detector

DEFLECTOR: (optional) NXdeflector

Deflectors outside the main optics ensembles described by the subclasses

LENS_EM: (optional) NXlens_em

Individual lenses outside the main optics ensembles described by the subclasses

FABRICATION: (optional) NXfabrication

RESOLUTION: (optional) NXresolution

Any other resolution not explicitly named in this base class.

Hypertext Anchors

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

NXDL Source:

https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/contributed_definitions/NXelectronanalyser.nxdl.xml