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The NIST Physics Program produces the most comprehensive set of reliable physical reference data available anywhere. The NIST collection of atomic energy levels, transition probabilities, and collision data is widely used by groups for characterizing and modeling all types of gaseous systems, including plasmas, planetary atmospheres, and astrophysical media, and for health physics applications. Databases and publications make these data easy to find and easy to use. The physics online databases have grown into an extensive listing. The NIST Chemistry WebBook now contains electronic and vibrational spectra for over 5000 compounds. The WebBook also contains constants of diatomic molecules.

NIST has also produced several important compilations of molecular data.

The codes in the list below have the following meanings:

PC PC product, most available for purchase, some are free
Online Free online system
DG Inclusion in the NIST Data Gateway - a portal providing access to many NIST scientific and technical databases. It is searchable by keyword, property, or substance name.
* Product contains data that have undergone rigorous critical evaluation by experienced researchers who recommend best values.
Online Subscription Product is a yearly subscription web product.

Physics Database
SRD 69 NIST Chemistry WebBook, Online, DG, *
SRD 64 NIST Elastic-Electron-Scattering Cross-Section Database, PC, DG, *
SRD 7 NIST Electron and Positron Stopping Powers of Materials, PC, DG, *
SRD 82 NIST Electron Effective-Attenuation-Length Database, PC, DG, *
SRD 71 NIST Electron Inelastic-Mean-Free-Path Database, PC, DG, *
SRD 105 Elemental Data Index, Online, DG, *
SRD 107 Electron-Impact Ionization Cross Section Database, Online, DG, *
SRD 108 Handbook of Basic Atomic Spectroscopic Data, Online, DG, *

SRD 160 FLYCHK Collisional-Radiative Code, Online, DG, *
SRD 158 SAHA Plasma Population Kinetics Database, Online, DG, *
SRD 159 NLTE4 Plasma Population Kinetics Database, Online, DG, *

Atomic Spectroscopic Data
SRD 141 Atomic Reference Data for Electronic Structure Calculation, Online, DG, *
SRD 78 Atomic Spectra Database, Online, DG, *
SRD 109 Atomic Spectral Line Broadening Bibliographic Database, Online, DG, *
SRD 110 Atomic Transition Probability Bibliographic Database, Online, DG, *
SRD 111 Ground Levels and Ionization Energies for the Neutral Atoms, Online, DG, *
SRD 112 Atlas of the Spectrum of Platinum/Neon Hollow-Cathode Lamp, Online, DG, *
SRD 128 X-Ray Transition Energies Database, Online, DG, *

Molecular Spectroscopic Data
SRD 114 Diatomic Spectral Database, Online, DG, *
SRD 115 Hydrocarbon Spectral Database, Online, DG, *
SRD 116 NIST Recommended Rest Frequencies for Observed Interstellar Molecular Microwave
, Online, DG, *
SRD 117 Triatomic Spectral Database, Online, DG, *
SRD 118 Wavenumber Tables for Calibration, Online, DG, *
SRD 119 Photoionization of CO2 (ARPES), Online, DG, *

Nuclear Physics
SRD 144 Atomic Weights & Isotopic Composition, Online, DG, *
SRD 120 Radionuclide Half-Life Measurements Online, DG, *

Physical Constants
SRD 121 Fundamental Physical Constants, Online, DG, *
SRD 122 International System of Units (SI), Online, DG, *
SRD 123 Searchable Bibliography on the Constants, Online, DG, *

Radiation Dosimetry
SRD 124 Stopping-Power and Range Tables for Electrons, Protons, and Helium Ions, Online, DG, *

X-Ray and Gamma-Ray Data
SRD 125 Bibliography of Photon Total Cross Section (Attenuation Coefficient)

Online, DG, *
SRD 8 XCOM: Photon Cross Sections Database, Online, DG, *
SRD 126 Tables of X-Ray Mass Attenuation Coefficients and Mass Energy Absorption Coefficients, Online, DG, *
SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables, Online, DG, *
SRD 128 X-Ray Transition Energies Database, Online, DG, *
SRD 20 NIST X-ray Photoelectron Spectroscopy Database 4.1, Online, DG, *