NXmpes¶
Status:
application definition, extends NXobject
Description:
Most general application definition for multidimensional photoelectron spectroscopy.
It can be used for ARPES, XPS, etc. More specialized application definitions are derived from it.
Symbols:
The symbols used in the schema to specify e.g. dimensions of arrays
nfa: Number of fast axes (acquired simutaneously) e.g. emission angle, kinetic energy
nsa: Number of slow axes (acquired scanning a physical quantity) e.g. lens voltage, spin direction
- Groups cited:
NXaperture, NXbeam, NXcalibration, NXcollectioncolumn, NXdata, NXdetector, NXelectronanalyser, NXenergydispersion, NXentry, NXinstrument, NXnote, NXprocess, NXsample, NXsource
Structure:
ENTRY: (required) NXentry
@entry: (required) NX_CHAR
NeXus convention is to use “entry1”, “entry2”, for analysis software to locate each entry.
@default: (optional) NX_CHAR
Default plottable NX data object.
title: (required) NX_CHAR
start_time: (required) NX_DATE_TIME
ISO8601 formatted date time of the start of the measurement.
definition: (required) NX_CHAR
Obligatory value:
NXmpes@version: (required) NX_CHAR
INSTRUMENT: (required) NXinstrument
SOURCE: (required) NXsource
The source used to generate the primary photons. Properties refer strictly to parameters of the source, not of the output beam. For example, the energy of the source is not the optical power of the beam, but the energy of the electron beam in a synchrotron and so on.
type: (required) NX_CHAR
Any of these values:
Synchrotron X-ray Source
Rotating Anode X-ray
Fixed Tube X-ray
UV Laser
Free-Electron Laser
Optical Laser
UV Plasma Source
Metal Jet X-ray
HHG lasername: (required) NX_CHAR
probe: (required) NX_CHAR
Type of probe. In photoemission it’s always photons, so the full NIAC list is restricted.
Any of these values:
x-ray|ultraviolet|visible lightBEAM: (required) NXbeam
distance: (required) NX_NUMBER {units=NX_LENGTH}
Distance of the point of evaluation of the beam from the sample surface.
incident_energy: (required) NX_NUMBER {units=NX_ENERGY}
In the case of a monchromatic beam this is the scalar energy. Several other use cases are permitted, depending on the presence of other incident_energy_X fields. In the case of a polychromatic beam this is an array of length m of energies, with the relative weights in incident_energy_weights. In the case of a monochromatic beam that varies shot-to-shot, this is an array of energies, one for each recorded shot. Here, incident_energy_weights and incident_energy_spread are not set. In the case of a polychromatic beam that varies shot-to-shot, this is an array of length m with the relative weights in incident_energy_weights as a 2D array. In the case of a polychromatic beam that varies shot-to-shot and where the channels also vary, this is a 2D array of dimensions nP by m (slow to fast) with the relative weights in incident_energy_weights as a 2D array. Note, variants are a good way to represent several of these use cases in a single dataset, e.g. if a calibrated, single-value energy value is available along with the original spectrum from which it was calibrated.
incident_energy_spread: (recommended) NX_NUMBER {units=NX_ENERGY}
The energy spread FWHM for the corresponding energy(ies) in incident_energy. In the case of shot-to-shot variation in the energy spread, this is a 2D array of dimension nP by m (slow to fast) of the spreads of the corresponding energy in incident_energy.
incident_energy_weights: (optional) NX_NUMBER {units=NX_ENERGY}
In the case of a polychromatic beam this is an array of length m of the relative weights of the corresponding energies in incident_energy. In the case of a polychromatic beam that varies shot-to-shot, this is a 2D array of dimensions np by m (slow to fast) of the relative weights of the corresponding energies in incident_energy.
incident_polarization[4]: (recommended) NX_NUMBER {units=NX_ANY}
Incident polarization specified as a Stokes vector.
@units: (required) NX_CHAR
The units for this observable are not included in the NIAC list. Responsibility on correct formatting and parsing is handed to the user by using ‘NX_ANY’. Correct parsing can still be implemented by using this attribute. Fill with: The unit unidata symbol if the unit has one (Example: ‘T’ for the unit of magnetic flux density tesla). The unit unidata name if the unit has a name (Example: ‘farad’ for capacitance). A string describing the units according to unidata unit operation notation, if the unit is a complex combination of named units and does not have a name. Example: for lightsource brilliance (SI) ‘1/(s.mm2.mrad2)’. Here: SI units are ‘V2/m2’.
ELECTRONANALYSER: (required) NXelectronanalyser
description: (required) NX_CHAR
Free text description of the type of detector.
energy_resolution: (required) NX_NUMBER {units=NX_ENERGY}
Energy resolution of the analyser with the current setting. May be linked from a NXcalibration.
fast_axes[nfa]: (optional) NX_CHAR
List of the axes that are acquired symultaneously 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: Hemispherical in ARPES mode: fast_axes: [energy,kx] Hemispherical with channeltron, sweeping energy mode: slow_axes: [energy] Tof: fast_axes: [energy, kx, ky] Momentum microscope, spin-resolved: fast_axes: [energy, kx, ky] slow_axes: [spin up-down, spin left-right] axes can 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[nsa]: (optional) NX_CHAR
List of the axes that are acquired by scanning a physical parameter, listed in order of decreasing speed. See fast_axes for examples.
COLLECTIONCOLUMN: (required) NXcollectioncolumn
scheme: (required) NX_CHAR
Scheme of the electron collection column.
Any of these values:
Standard
Deflector
PEEM
Momentum Microscopemode: (recommended) NX_CHAR
Labelling of the lens setting in use.
projection: (recommended) NX_CHAR
The space projected in the angularly dispersive directions, i.e. real or reciprocal.
Any of these values:
real|reciprocalENERGYDISPERSION: (required) NXenergydispersion
scheme: (required) NX_CHAR
Energy dispersion scheme employed.
Any of these values:
tof
hemispherical
double hemispherical
cylindrical mirror
display mirror
retarding gridpass_energy: (required) NX_NUMBER {units=NX_ENERGY}
energy of the electrons on the mean path of the analyser. Pass energy for hemispherics, drift energy for tofs.
energy_scan_mode: (required) NX_CHAR
Way of scanning the energy axis (fixed or sweep).
Any of these values:
fixed|sweepAPERTURE: (recommended) NXaperture
Aperture generating the momentum and/or energy filtering.
description: (required) NX_CHAR
Type of aperture inserted in the beam.
Any of these values:
slit|pinhole|irisshape: (required) NX_CHAR
Description of the shape of the active part of the aperture, curved or straight for horizontal slits, square or round for pinhole etc.
Any of these values:
curved
straight
circle
square
hexagon
octagon
bladedsize: (required) NX_NUMBER {units=NX_LENGTH}
The relevant dimension for the aperture (slit width, pinhole diameter etc).
DETECTOR: (required) NXdetector
amplifier_type: (recommended) NX_CHAR
Type of electron amplifier in the first amplification step.
Any of these values:
MCP|channeltrondetector_type: (required) NX_CHAR
Description of the detector type.
Any of these values:
DLD
Phosphor+CCD
Phosphor+CMOS
ECMOS
Anode
Multi-anodeDATA: (recommended) NXdata
PROCESS: (required) NXprocess
calculated_energy[ne]: (optional) NX_FLOAT {units=NX_ENERGY}
Calibrated energy axis.
energy_calibration: (required) NXcalibration
applied: (required) NX_BOOLEAN
Has an energy calibration been applied?
SAMPLE: (required) NXsample
name: (required) NX_CHAR
chemical_formula: (required) NX_CHAR
preparation_date: (recommended) NX_DATE_TIME
ISO 8601 date of preparation of the sample for the XPS experiment (i.e. cleaving, last annealing).
temperature: (required) NX_NUMBER {units=NX_TEMPERATURE}
In the case of a fixed temperature measurement this is the scalar temperature of the sample. In the case of an experiment in which the temperature is changed and recoded, this is an array of length m of temperatures.
situation: (required) NX_CHAR
pressure: (required) NX_NUMBER {units=NX_PRESSURE}
In the case of a fixed pressure measurement this is the scalar pressure. In the case of an experiment in which pressure changes, or anyway it is recorded, this is an array of length m of pressures.
sample_history: (recommended) NXnote
A descriptor to keep track of the treatment of the sample before entering the photoemission experiment. Ideally, a full report of the previous operations, in any format (NXnote allows to add pictures, audio, movies). Alternatively, a reference to the location or a unique identifier or other metadata file. In the case these are not available, free-text description.
preparation_description: (required) NXnote
Description of the surface preparation technique for the XPS experiment, i.e. UHV cleaving, in-situ growth, sputtering/annealing etc. Ideally, a full report of the previous operations, in any format(NXnote allows to add pictures, audio, movies). Alternatively, a reference to the location or a unique identifier or other metadata file. In the case these are not available, free-text description.
DATA: (required) NXdata
Hypertext Anchors¶
Table of hypertext anchors for all groups, fields, attributes, and links defined in this class.
