One of the most exciting discoveries of contemporary observational astronomy has been that the interstellar medium contains a large number of sometimes complex molecules in various isotopic and isomeric forms. These molecules are observed in the microwave and infrared part of the electromagnetic spectrum, owing to rotational transitions. In the case of shock heated regions, they may also be observed in the infrared through vibrational transitions. Visual and ultraviolet electronic transitions are observed in absorption along lines of sight to bright, hot stars.

The interpretation of these observations and the elucidation of the processes leading to the formation of these molecules requires a great deal of atomic and molecular data. Laboratory experiments and theoretical calculations are performed in order to understand the physics of the processes that lead to the formation of these molecules.

Another recent surprising discovery is vacuum ultraviolet (VUV) emission from the tails of earth-passing comets such as Hale-Bopp and Hyakutake. The emission results from electron transfer between multicharged solar wind ions (O, He, and Ne) and neutrals in the cometary tails. Accurate knowledge of the underlying processes would not just allow for explaining the observations but might enable the use of the VUV emission as a diagnostics tool for charge state and flux distributions of the solar wind ions.