Molecular spectra databases now available online. (General Developments).

NIST has made available on the Web three linked databases of the microwave and RF spectra of diatomic, triatomic, and hydrocarbon molecules. Originally published as spectral tables in the Journal of Physical and Chemical Reference Data, the online version includes additional molecules and allows advanced browsing and searching of the data by molecular species, type, or frequency.

Rotational spectral lines for 121 diatomic molecules, 55 triatomic molecules, and 91 hydrocarbon molecules are included. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty, and reference are given for each transition. The spectral lines for many molecules and normal isotopic species have been refit to produce a comprehensive and consistent analysis of all the data obtained from many sources. The derived molecular properties, such as rotational and centrifugal distortion constants, hyperfine structure constants, electric dipole moments, rotational g-factors and internuclear distances (for diatomic molecules) are listed with one standard deviation uncertainties for all species.

The Diatomic, Triatomic, and Hydrocarbon Spectra Databases can be accessed on the Web at http:// physics.nist.gov/MWtables. Further information on additional molecular spectroscopic databases developed by ECSED is available at http://physics.nist.gov/data. Development of these databases was supported in part by the Standard Reference Data Program (SRDP) and by NISTs Systems Integration for Manufacturing Applications (SIMA) Program.

CONTACTS: Frank Lovas, [phone]; francis. [e-mail] or Karen Olsen, [phone]; [e-mail].