Physical Reference Data 

Elemental Data Index

Provides access to the holdings of NIST Physical Measurement Laboratory online data organized by element.

Periodic Table: Atomic Properties of the Elements

Contains NIST critically-evaluated data on atomic properties of the elements.
Suitable for high-resolution color printing for desk or wall-chart display. 

Physical Constants  

Contains values of the fundamental physical constants and a related bibliographic database.

Atomic Spectroscopy Data  

Contains databases for energy levels, wavelengths, and transition probabilities for atoms and ions and related bibliographic databases.

Molecular Spectroscopic Data  

Includes databases containing spectroscopic data for small molecules, hydrocarbons, and interstellar molecules. In addition, there are two publications containing equations and the underpinning theory for molecular spectroscopy.

Atomic and Molecular Data  

Contains databases on thermophysical properties of gases, electron-impact cross sections (of atoms & molecules), potential energy surfaces of group II dimers, and atomic weights and isotopic compositions.

X-Ray and Gamma-Ray Data  

Contains databases on the interaction of x-rays and gamma-rays with elements and compounds.

Radiation Dosimetry Data  

This database calculates stopping-power and range tables for electrons, protons, or helium ions.

Nuclear Physics Data  

Contains a table of the half lives of 65 radionuclides and a database of the isotopic compositions, atomic weights and relative atomic masses of the elements.

Condensed Matter Physics Data  

This database consists of evaluated data for use in total-energy calculations of electronic structure by density-functional theory. It contains total energies and orbital energy eigenvalues for all atoms from hydrogen to uranium.

Other NIST Data 

Provides access to all data sets at NIST.