A LABORATORY DATABASE OF SOLID CO AND CO2 FOR ISO

We present laboratory measured infrared spectra of mixtures containing CO and CO2 at low temperatures. The pro- files and peak position of the absorption features due to these species are very sensitive to molecular environment, tempera- ture, irradiation history and particle shape. Illustrative examples of these variations are briefly discussed. We have compiled datafiles containing the laboratory spec- tra, 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 ehrenfreund isodb. To- gether 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.