Refractive Indices and Infrared Band Strengths of Amorphous Ices of Key Fluorinated Refrigerants 1,1,1,2-Tetrafluoroethane, 2,3,3,3-Tetrafluoropropene, and 3,3,3-Trifluoropropene.

Hydrofluorocarbons (HFCs), a class of polyfluorocarbon (PFC), represent a key group of chemicals exploited extensively in refrigeration and innovative future technological cooling applications. To separate, purify, and reuse HFCs, spectroscopic properties of these compounds must be available. To quantify these materials under cryogenic conditions, a condensed-phase spectroscopic investigation of their physical parameters is required. Herein, the optical and spectroscopic properties of HFCs used as refrigerant at low temperature (10 K) are investigated. Refractive indices of 1,1,1,2-tetrafluoroethane (CF3CH2F; HFC134a), 2,3,3,3-tetrafluoropropene (CF3CF=CH2; R1234yf), and 3,3,3-trifluoropropene (CF3CH=CH2; R1243zf) are found to be 1.24 ± 0.02, 1.34 ± 0.02, and 1.30 ± 0.02, respectively. Infrared band strengths of the abovementioned HFC ices on a cold silver substrate are measured utilizing absorption reflection infrared spectroscopy. The fundamental vibrational modes are analyzed using quantum chemical calculations in tandem with vibrational spectroscopic analysis. The strongest infrared absorption corresponds to combined CF vibrational modes originating from CF3 group and olefinic CF bonds, which has band strengths ranging 2 × 10-18 to 3 × 10-18 cm molecule-1. Comparisons of solid and vapor-phase spectra show vibrational shifts, aiding understanding of solid-state interactions and ice formation. These findings enhance knowledge of low-temperature HFC chemistry, focusing on optical and spectroscopic changes during ice development.