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, radiative transition probabilities, and ionization energies 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 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.

The use of International Units and the expression of uncertainty in measurement is critical to all data activities. For information on these topics, see guidelines for evaluating and expressing measurement uncertainty, and information on the International System of Units (SI).