Fundamental Physical Constants from NIST - The values of the fundamental physical constants provided at this site are recommended for international use by CODATA and are the latest available. NIST Physical Reference Data - Database holding information on fundamental physical constants, atomic spectra, molecular spectroscopic data, ionization data, X-Ray and Gamma-Ray data, radiation dosimetry data, nuclear physics data, and condensed matter physics data. JPL Molecular Spectroscopy - Database which has an extensive library including programs for fitting spectra and spectral line files for a large number of molecules. Use requires knowledge of spectroscopy and quantum mechanics. National Institute of Standards and Technology WebBook - Thermochemical data for over 6000 organic and small inorganic compounds. Reaction thermochemistry data for over 9000 reactions. IR spectra for over 8700 compounds. Mass spectra for over 12,000 compounds. UV/Vis spectra for over 400 compounds. Electronic and vibrational spectra for over 4000 compounds. Constants of diatomic molecules (spectroscopic data) for over 600 compounds. Ion energetics data for over 16,000 compounds. Thermophysical property data for 33 fluids. GRI-Mech - At Berkeley, also has selected kinetic rate constants and parameters for reactions involving the species included in their database. Surface Tension Data - Surface tension values of some common test liquids for surface energy analysis. Quantum Chemistry Literature DataBase - A literature database on ab initio MO calculations published in major journals of Chemistry, Physics and Computer Science since 1978.