2012MNRAS.423.2868I

The infrared spectra, as well as the integrated molar absorptivity (Ψ) and the molar extinction coefficient (ε) of each infrared transition of the hydrogenated fullerenes (known as fulleranes) C₆₀H₃₆, C₆₀H₁₈ and C₇₀H₃₈, and a mixture of fulleranes generally referred to as 77 per cent of C₆₀H_x and 22 per cent C₇₀H_ywith x ≈ y > 30, are presented and discussed. These data are useful for the search, identification and quantitative determination of fulleranes in space after the recent discovery that their parent molecules, C₆₀ and C₇₀, are more abundant in space than initially thought, being present in a variety of H-rich circumstellar environments such as planetary nebulae and only mild H-deficient R Coronae Borealis stars, and in the interstellar medium. It is shown that the C–H stretching band of the fulleranes C₆₀H₃₆, C₆₀H₁₈ and C₇₀H₃₈, and their mixture may be most useful for the identification of these molecules because their Ψ and ε values are unique in terms of strength, overcoming by far the typical Ψ and ε values of reference molecules such as adamantane and docosane, as well as typical ε literature data for aliphatic molecules. In contrast to the rather simple infrared spectra of C₆₀H₃₆ and C₆₀H₃₈, the infrared spectra of two C₆₀H₁₈isomers are reported as characterized by a rich number of bands which may allow an easier identification than the higher homologues. The dependence of the infrared bands of fulleranes on temperature was studied over a wide range of temperatures (from -180°C to +250°C) and extrapolated to 0 K. Probing the time variability of five Fe low broad absorption-line quasars