Information on Molecules and Atoms.

Rest frequencies and other parameters can be found in:

Molecular Spectroscopy Home Page (JPL)

Lovas' List of Recommended Rest Frequencies

Infrared Line Lists for Atoms and Molecules (MPE, Garching)

Worldwide Molecular Astrophysics Resources (Leiden)

The Cologne Database for Molecular Spectroscopy

Other Information on molecules of some use:

To do some Calculations: