Broadband UV–Visible Refractive Index Measurements for Astrophysics and Planetary Science

For accurate interpretation of JWST ice spectra, radiative transfer models are required. These models need optical constants which are derived from laboratory experiments. Within the Optical Analysis Setup for Interstellar Spectroscopy (OASIS), interstellar environments are simulated by forming ice at low temperatures (10 K) within an ultra-high vacuum chamber (1E-8 mbar). Using background deposition, the real refractive index is measured as the ice grows in the chamber. Refractive index curves are calculated from the data, giving a refractive index from 250 nm up to 800 nm in a single experiment. Pure and binary ices are formed at different temperatures, allowing for the study of porosity behaviour across different temperature regimes. Different mixing ratios of binary ices such as water and carbon dioxide are studies to observe the behaviour of the real refractive index. We find similar values as previously reported and expand the explored parameter space of different mixing ratios at different temperatures.