Infrared spectra and optical constants of astronomical ices: V . cyclopropane and ethylene oxide

Infrared (IR) spectra of solid cyclopropane ( c -C 3 H 6 ) and ethylene oxide ( c -C 2 H 4 O), two cyclic aliphatic compounds, have been recorded in their amorphous and crystalline states. The spectra have been combined with measurements of density and refractive index (λ = 670 nm) for each form of each solid to compute IR intensities (i.e., absorption coefficients and band strengths) and optical constants for use in laboratory experiments and astronomical observations. These are the first such measurements of absolute IR intensities and optical constants for each solid at temperatures relevant to the outer Solar System and the interstellar medium, with all results coming from a single laboratory. Two literature band strengths for ethylene oxide's strongest IR feature, one value a calculation and the other a gas-phase measurement, need to be increased by ∼25% to match the solid-phase value reported here. Suggestions are made for applications and future work related to the chemistry of icy bodies in the Solar System and beyond, including Pluto's surface, Titan's atmosphere, and the formation of cometary C 3.