Attributes

Every SpinData object carries two attribute dictionaries that travel with the data through the entire processing workflow:

  • ``attrs`` — the raw experimental parameters read directly from the spectrometer file. Keys and values are instrument-specific (e.g. Bruker BES3T uses "MF" for microwave frequency, TopSpin uses "SFO1").

  • ``spinlab_attrs`` — a normalized layer that SpinLab populates automatically on import. It maps the instrument-specific keys to a common, format-independent set of names so that the same code works regardless of which instrument produced the data.

Both dictionaries are plain Python dict objects and can be read, updated, or extended at any time:

# Read a raw attribute
print(data.attrs["MF"])              # Bruker WinEPR microwave frequency

# Read a normalized SpinLab attribute
print(data.spinlab_attrs["frequency"])   # same value, any format

# Print all raw attributes in a formatted table
data.exp_info()

# Print all SpinLab attributes
data.spinlab_info()

SpinLab Attributes (spinlab_attrs)

The following attributes are automatically extracted and normalized on import. A value of None means the attribute is not available for a particular format.

Attribute

Unit

Available for

Description

experiment_type

—

All formats

String identifying the experiment type. Set automatically on import and used by sl.fancy_plot() to select axis labels and formatting. Can be changed manually (see below).

data_format

—

All formats

Name of the file format that was imported (e.g. "XEPR", "TopSpin", "WinEPR").

data_type

—

All formats

Technique: "EPR" or "NMR".

scans

—

All formats

Number of scans or averages accumulated.

frequency

Hz

All formats

Microwave frequency (EPR) or NMR Larmor frequency. Stored in Hz after unit conversion.

power

W

EPR, RS2D

Microwave or RF power.

attenuation

dB

EPR (Xepr, Xenon, WinEPR, ESP, RS2D)

Attenuator setting.

pulse_attenuation

dB

EPR (Xepr, Xenon)

Pulse attenuator setting (pulsed EPR).

center_field

mT

EPR

Center magnetic field of the sweep.

sweep_field

mT

EPR, VnmrJ, TNMR, SpecMan

Total field sweep width (EPR) or spectral width (NMR).

repetition_time

s

NMR (Prospa, Delta, VnmrJ, TNMR), SpecMan

Repetition time between successive scans.

receiver_gain

—

EPR (WinEPR, ESP), NMR (Delta, TNMR), RS2D

Receiver gain setting.

receiver_attenuation

dB

(reserved, currently None for all formats)

Receiver attenuation.

conversion_time

ms

EPR (Xepr, Xenon, WinEPR, ESP)

ADC conversion time per point (CW EPR).

time_constant

ms

EPR (Xepr, Xenon, WinEPR, ESP)

Filter time constant (CW EPR).

modulation_amplitude

mT

EPR (Xepr, Xenon, WinEPR, ESP)

Field modulation amplitude (CW EPR).

modulation_frequency

kHz

EPR (Xepr, Xenon, WinEPR, ESP)

Field modulation frequency (CW EPR).

temperature

K

EPR (Xepr, Xenon, WinEPR, ESP), NMR (Delta, VnmrJ, TNMR)

Sample temperature.

dwell_time

s

RS2D

Dwell time between digitizer samples.

The experiment_type Attribute

experiment_type is the most important attribute in SpinLab. It is stored in attrs (not spinlab_attrs) and controls how sl.fancy_plot() formats the figure — which axis labels, title, and marker style are applied.

SpinLab sets it automatically on import based on the file format. You can inspect or change it at any time:

print(data.attrs["experiment_type"])          # e.g. 'epr_spectrum'

# Override to use a different plot style
data.attrs["experiment_type"] = "inversion_recovery"

The following values are currently defined:

experiment_type

Technique

Description

epr_spectrum

EPR

Continuous-wave EPR spectrum. Default when a CW EPR file is loaded. X-axis: magnetic field (mT).

epr_transient

EPR

EPR transient from a transient recorder. X-axis: time (µs).

epr_transient_E580

EPR

EPR transient specific to the Bruker E580 spectrometer. X-axis: time (ns).

echo_decay

EPR

Echo intensity as a function of pulse separation. X-axis: time (s).

eldor_profile

EPR

ELDOR profile. X-axis: pump frequency (GHz).

saturation_recovery

EPR

Saturation recovery experiment. X-axis: evolution time (s).

inversion_recovery

NMR

Inversion recovery experiment. X-axis: evolution time T1 (s).

polarization_buildup

DNP

DNP polarization build-up. X-axis: contact time (s).

enhancements_P

DNP

DNP enhancement factor vs. microwave power. X-axis: power (dBm).

enhancements_PdBm

DNP

DNP enhancement factor vs. microwave power in dBm. X-axis: power (dBm).

enhancements_PW

DNP

DNP enhancement factor vs. microwave power in Watts. X-axis: power (W).

sl_enhancement_profile_f

DNP

Spin enhancement profile vs. frequency. X-axis: frequency (GHz).

Accessing Attributes

import spinlab as sl

data = sl.load("spectrum.DTA")

# --- Raw attrs ---
print(data.attrs)                        # full dictionary
data.exp_info()                          # formatted table printout

print(data.attrs["experiment_type"])     # 'epr_spectrum'
print(data.attrs["frequency"])           # microwave frequency (raw)
print(data.attrs["nscans"])              # number of scans (Xepr raw key)

# --- SpinLab attrs ---
print(data.spinlab_attrs)                # full dictionary
data.spinlab_info()                      # formatted table printout

print(data.spinlab_attrs["frequency"])   # same frequency value, normalized
print(data.spinlab_attrs["scans"])       # number of scans, any format
print(data.spinlab_attrs["temperature"]) # temperature in K

# --- Both together ---
data.show_attrs()                        # prints spinlab_attrs + proc_attrs

Modifying Attributes

Attributes can be added or changed freely. A common use case is correcting the experiment_type or adding custom metadata before saving:

# Change experiment type for fancy_plot formatting
data.attrs["experiment_type"] = "echo_decay"

# Add a custom annotation
data.attrs["sample_name"] = "TEMPO in toluene"
data.attrs["concentration_mM"] = 0.5

# Save with the updated attributes — all attrs are preserved in HDF5
sl.save(data, "annotated_data.h5")

Further Reading