The Cologne Database for Molecular Spectroscopy, CDMS: a useful tool for astronomers and spectroscopists

The general features of the internet browser-accessible Cologne Database for Molecular Spectroscopy (CDMS) and recent developments in the CDMS are described in the present article. The database consists of several parts; among them is a catalog of transition frequencies from the radio-frequency to the far-infrared region covering atomic and molecular species that (may) occur in the interstellar or circumstellar medium or in planetary atmospheres. As of December 2004, 280 species are present in this catalog. The transition frequencies were predicted from fits of experimental data to established Hamiltonian models. We present some examples to demonstrate how the combination of various input data or a compact representation of the Hamiltonian can be beneficial for the prediction of the line frequencies.