2.3.3.3.122. NXenergydispersion¶
Status:
base class, extends NXobject
Description:
Subclass of NXelectronanalyser to describe the energy dispersion section of a ...
Subclass of NXelectronanalyser to describe the energy dispersion section of a photoelectron analyser.
Symbols:
No symbol table
- Groups cited:
NXaperture, NXdeflector, NXfabrication, NXlens_em, 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.
scheme: (optional) NX_CHAR
Energy dispersion scheme employed, for example: tof, hemispherical, cylindrica ...
Energy dispersion scheme employed, for example: tof, hemispherical, cylindrical, mirror, retarding grid, etc.
pass_energy: (optional) NX_FLOAT {units=NX_ENERGY}
Mean kinetic energy of the electrons in the energy-dispersive portion of the a ...
Mean kinetic energy of the electrons in the energy-dispersive portion of the analyser. This term should be used for hemispherical analysers.
This concept is related to term 12.63 of the ISO 18115-1:2023 standard.
kinetic_energy: (optional) NX_FLOAT {units=NX_ENERGY}
Kinetic energy set for the dispersive analyzer section. Can be either the set ...
Kinetic energy set for the dispersive analyzer section. Can be either the set kinetic energy, or the whole calibrated energy axis of a scan.
drift_energy: (optional) NX_FLOAT {units=NX_ENERGY}
Drift energy for time-of-flight energy dispersive elements.
center_energy: (optional) NX_FLOAT {units=NX_ENERGY}
Center of the energy window
energy_interval: (optional) NX_FLOAT {units=NX_ENERGY}
The interval of transmitted energies. It can be two different things depending ...
The interval of transmitted energies. It can be two different things depending on whether the scan is fixed or swept. With a fixed scan it is a 2 vector containing the extrema of the transmitted energy window (smaller number first). With a swept scan of m steps it is a 2xm array of windows one for each measurement point.
diameter: (optional) NX_FLOAT {units=NX_LENGTH}
Diameter of the dispersive orbit
radius: (optional) NX_FLOAT {units=NX_LENGTH}
Radius of the dispersive orbit
energy_scan_mode: (optional) NX_CHAR
Way of scanning the energy axis ...
Way of scanning the energy axis
Any of these values:
fixed_analyser_transmission: constant \(\Delta E\) mode, where the electron retardation (i.e., the fraction of pass energy to kinetic energy, \(R = (E_K - W/E_p)\), is scanned, but the pass energy \(E_p\) is kept constant. Here, \(W = e \phi\) is the spectrometer work function (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). This mode is often used in XPS/UPS because the energy resolution does not change with changing energy (due to the constant pass energy). Synonyms: constant \(\Delta E\) mode, constant analyser energy mode, CAE mode, FAT mode This concept is related to term 12.64 of the ISO 18115-1:2023 standard.
fixed_retardation_ratio: constant \(\Delta E/E\) mode, where the pass energy is scanned such that the electron retardation ratio is constant. In this mode, electrons of all energies are decelerated with this same fixed factor. Thus, the pass energy is proportional to the kinetic energy. This mode is often used in Auger electron spectroscopy (AES) to improve S/N for high-KE electrons, but this leads to a changing energy resolution (\(\Delta E \sim E_p\)) at different kinetic energies. It can however also be used in XPS. Synonyms: constant \(\Delta E/E\) mode, constant retardation ratio mode, CRR mode, FRR mode This concept is related to term 12.66 of the ISO 18115-1:2023 standard.
fixed_energy: In the fixed energy (FE) mode, the intensity for one single kinetic energy is measured for a specified time. This mode is particulary useful during setup or alignment of the electron analyzer, for analysis of stability of the excitation source or for sample alignment. Since the mode measures intensity as a function of time, the difference in channel signals is not of interest. Therefore, the signals from all channels are summed. Synonyms: FE mode
snapshot: Snapshot mode does not involve an energy scan and instead collects data from all channels of the detector without averaging. The resulting spectrum reflects the energy distribution of particles passing through the analyzer using the current settings. This mode is commonly used to position the detection energy at the peak of a peak and record the signal, enabling faster data acquisition within a limited energy range compared to FAT. Snapshot measurements are particularly suitable for CCD and DLD detectors, which have multiple channels and can accurately display the peak shape. While five or nine-channel detectors can also be used for snapshot measurements, their energy resolution is relatively lower.
dither: In dither acquisition mode, the kinetic energy of the analyzer is randomly varied by a small value around a central value and at fixed pass energy. This allows reducing or removing inhomogeneities of the detector efficiency, such as e.g. imposed by a mesh in front of the detector. Mostly relevant for CCD/DLD type of detectors.tof_distance: (optional) NX_FLOAT {units=NX_LENGTH}
Length of the tof drift electrode
depends_on: (optional) NX_CHAR
Specifies the position of the energy dispesive elemeent by pointing to the las ...
Specifies the position of the energy dispesive elemeent by pointing to the last transformation in the transformation chain in the NXtransformations group.
APERTURE: (optional) NXaperture
Size, position and shape of a slit in dispersive analyzer, e.g. entrance and ...
Size, position and shape of a slit in dispersive analyzer, e.g. entrance and exit slits.
DEFLECTOR: (optional) NXdeflector
Deflectors in the energy dispersive section
LENS_EM: (optional) NXlens_em
Individual lenses in the energy dispersive section
FABRICATION: (optional) NXfabrication
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 energy dispersive element 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.
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