A New Method for Measuring Infrared Band Strengths in H 2 O Ices: First Results for OCS, H 2 S, and SO 2

Infrared (IR) band strengths are needed to extract accurate molecular abundances from astronomical observations of interstellar and solar system ices. However, laboratory measurements of such intensities often have required multiple assumptions about ice composition and thickness. Here we describe a method that circumvents most of the common assumptions and uncertainties in IR band-strength determinations. We have applied the method to measure IR band strengths of OCS, H2S, and SO2 in the absence and presence of H2O ice at 10 K, the first measurements of their type. Our results show for the first time that the presence of H2O makes little difference in IR intensities for these three sulfur-containing molecules' strongest IR features. The immediate application will be to laboratory studies of low-temperature chemistry of interstellar and cometary ices.