Leiden Atomic and Molecular Database
LAMDA | Atomic datafiles | Molecular datafiles | Data format

A wide variety of molecules has been detected in space to date ranging from simple molecules like CO to more complex organic molecules like ethers and alcohols. Observations of molecular lines at millimetre and infrared wavelengths, supplemented by careful and detailed modelling, are a powerful tool to investigate the physical and chemical conditions of astrophysical objects.

To extract astrophysical parameters, the excitation and radiative transfer of the lines needs to be calculated. This requires accurate molecular data in the form of energy levels, statistical weights and transition frequencies as well as the spontaneous emission probabilities and collisional rate coefficients. The JPL catalogue, HITRAN database, and the CDMS catalogue contain energy levels and transition strenghts for a large number of molecular species. Collisional rate coefficients usually pose the largest source of uncertainty of the molecular data input. Calculated rates are also only available for a very limited number of molecules and typically evaluated in a narrow range of temperatures and including few energy levels.

Presented here is the first effort to systematically collect and present the data in a form easily used in radiative transfer modelling of interstellar regions. Extrapolation of collisional rate coefficients are also presented. At present focus is on rotational transitions within the ground vibrational state.

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