SIMBAD references

Water ice is the most important component in astrophysical ices and is characterized by a strong broad absorption at 3µm, observed in many interstellar spectra. In specific interstellar environments grain mantles might contain only a small amount of water, which is diluted in other volatiles dominant in these regions (e.g. CO, O₂, N₂, CO₂). Theoretical models suggest that interstellar mantles are rich in non-detected molecules such as O₂ and N₂. If water is diluted in non-polar matrices the water molecules display very sharp discrete bands due to the monomeric and dimeric H₂O. These peculiar bands lie between 2.5 and 2.9µm, shortward of the 3µm polymeric H₂O ice band. We have performed a detailed study of the infrared properties of H₂O diluted in various concentrations and matrices containing Ar, CO, CO₂, O₂, N₂ and naphthalene. Each molecule present in the matrix has its individual fingerprint in the spectrum of isolated H₂O and can be traced by the resulting band position of the individual H₂O molecules and overall pattern of the infrared spectrum. The concentration of H₂O in the matrix determines the specific intensity ratios of the monomeric, dimeric and polymeric water bands. We discuss the possible detection of isolated water on low temperature and ultraviolet shielded grain mantles covered with non-polar ices. Together with astronomical spectra taken by the ISO satellite these laboratory data will be extremely valuable for the determination of the grain mantle composition in dense clouds. Due to the unique spectral signature of H₂O/CO/O₂ mixtures the detection of isolated water may allow us to infer the presence and abundance of solid O₂.