A laboratory database of solid CO and CO2 for ISO

We present laboratory measured infrared spectra of mixtures containing CO and CO:! at low temperatures. The profiles and peak position of the absorption features due to these species are very sensitive to molecular environment, temperature, irradiation history and particle shape. Illustrative examples of these variations are briefly discussed. We have compiled datafiles containing the laboratory spectra, derived optical constants, as well as extinction efficiency calculations for small grains. These files can be retrieved from the WWW in various formats after November 1st, 1996, under http://www.strw.leidenuniv.nl/similar to ehrenfreund/isodb. Together with astronomical spectra taken by the ISO satellite these laboratory data will be valuable for the determination of the grain mantle composition and grain evolution in dense clouds.