The internet browser-accessible Cologne Database for Molecular Spectroscopy, CDMS, 1 ; 2 contains as one main part a catalog of rotational transition frequencies of molecular species that have been or may be identified in the interstellar medium, circumstellar envelopes, or planetary atmospheres. Rovibrational transitions in the far- and mid- infrared regions are currently available to a limited extent, but their importance will likely increase. Separate entries are provided for minor isotopic species or for molecules in excited vibrational states as far as appropriate. The entries have been created by fitting critically evaluated experimental data, mostly from laboratory experiments, to suitable Hamiltonian models to ensure entries as reliable as possible. Particular emphasis has been put on supplying data in the (sub-) millimeter and terahertz regions for telescopes such as APEX and the SMA as well as for the upcoming Herschel mission and ALMA.
The catalog is updated continuously. As of January 2006, the catalog contains more than 350 species of astrophysical, astrochemical, and planetary interest. It is available online free of charge through a link on the KOSMA web-site http://www.ph1.uni- koeln.de/ or via the short-cut http://www.cdms.de/.
Transitions of molecules vibrationally or highly rotationally excited are particularly strong toward high-mass star-forming regions where also complex molecules are sought. Further rotational and rovibrational spectroscopic data are needed in order to charac- terize these states.
The CDMS also includes a web page listing molecules detected in astronomical sources, a help page for fitting rotationally resolved spectra, as well as information on recent changes in the database.