Infrared spectra and optical constants of astronomical ices: II. Ethane and ethylene

• Mid- and near-IR spectra were measured for ethane and ethylene ices at 10–60 K.
• Refractive indices for each ice’s phases were measured at a specific temperature.
• Infrared optical constants, n and k, were calculated for ethane and ethylene ices.
• Our results were compared to those in the literature where available.
• All of our results are electronically available.

Infrared spectroscopic observations have established the presence of hydrocarbon ices on Pluto and other TNOs, but the abundances of such molecules cannot be deduced without accurate optical constants (n, k) and reference spectra. In this paper we present our recent measurements of near- and mid-infrared optical constants for ethane (C2H6) and ethylene (C2H4) in multiple ice phases and at multiple temperatures. As in our recent work on acetylene (C2H2), we also report new measurements of the index of refraction of each ice at 670 nm. Comparisons are made to earlier work where possible, and electronic versions of our new results are made available.