Elements

The JSON file containing most of the information on chemical elements is downloaded from the PubChem website : https://pubchem.ncbi.nlm.nih.gov/rest/pug/periodictable/JSON/?response_type=save&response_basename=PubChemElements_all

Units were added manually and column names have been modified.

You can access their interactive periodic table and find all relevant references here: https://pubchem.ncbi.nlm.nih.gov/periodic-table/#view=table.

X-Ray data

X-ray data are extracted from the X-RAY DATA BOOKLET.

References:

J. A. Bearden, “X-Ray Wavelengths,” Rev. Mod. Phys. 39, 78 (1967).
M. O. Krause and J. H. Oliver, “Natural Widths of Atomic K and L Levels, Ka X-Ray Lines and Several KLL Auger Lines,” J. Phys. Chem. Ref. Data 8, 329 (1979).

Isotopes

Isotope ground state properties are extracted from:

NUDAT3
The unrounded Atomic Mass Evaluation 2020 table for mass excesses and uncertainties, downloaded from the official IAEA mirror as mass_1.mas20.txt.
The IAEA Nuclear Charge Radii table for the published Angeli–Marinova charge radii.
The IAEA recommended nuclear moments tables for magnetic-dipole and electric-quadrupole moments.

TkN uses the NuDat JSON as the authority for isotope discovery years. Recommended moments are assigned either to the ground state or, when the state can be matched unambiguously, to the corresponding ENSDF adopted level. Static moments incompatible with the level spin are rejected.

Exact local source snapshots are installed as fallbacks. Each online download is validated and compared with the fallback; changed sources are proposed for review by the monthly database automation.

Levels and decays

Excited states and decay information are extracted from ENSDF and XUNDL databases.

Contributions to ENSDF are made by members of NSDD, the international network of Nuclear Structure and Decay Data evaluators.

Data update

The TkN database is automatically updated every month (the 15th) to take into account new data releases from NuDat, AME, the IAEA charge-radii and moments tables, and ENSDF/XUNDL.

A primary-source-only change never replaces a different public SQLite artifact under an unchanged ENSDF/XUNDL-derived filename. It is retained first as a reviewed versioned fallback and enters the published database with the next uniquely named database release, pending a future explicit artifact-revision contract.

The database history records the additions, removals and modifications between successive published databases. Detailed changes are available by nucleus, dataset, level and transition.