Infrared spectroscopic observations toward objects obscured by dense cloud material show that H₂O, CO and, likely, CO₂ are important constituents of interstellar ice mantles. In order to accurately calculate the column densities of these molecules, it is important to have good measurements of their infrared band strengths in astrophysical ice analogs. We present the results of laboratory experiments to determine these band strengths. Improved experimental methods, relying on simultaneous independent depositions of the molecule to be studied and of the dominating ice component, have led to accuracies better than a few percent. Furthermore, the temperature behavior of the infrared band strengths of CO and H₂O are studied. In contrast with previous work, the strengths of the CO, CO₂, and H₂O infrared features are found to depend only weakly on the composition of the ice matrix, and the reversible temperature dependence of the CO band is found to be weaker than previously measured for a mixture of CO in H₂O.
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Gerakines et al. (1994) studied this question.