Infrared spectra of solid indene pure and in water ice: implications for observed IR absorptions in TMC-1

ABSTRACT Experimental and theoretical infrared spectra, between 4000 500 cm−1 (2.5–20 μm), band strengths of two solid phases indene, amorphous, crystalline, are given for the first time. The samples were generated via vapour deposition under high vacuum conditions on a cold surface. Density functional theory was employed calculations (IR) spectra. For lack previous information, monoclinic symmetry is suggested crystalline phase based comparison calculated experimental IR Assignments, calculations, main indene absorptions. spectra highly diluted mixtures in amorphous water at 10 K also provided, evidencing that spectrum not much altered by ice environment. These data expected to be useful search this species astrophysical environments with JWST. With obtained work, applying simple literature model, we find could represent most 2–5 per cent intensity weak absorption feature 3.3 μm recently reported Elias 16. A column density (1.5–0.6) × 1016 cm−2 estimated mantles TMC-1. It would correspond ≈ (2–0.8) 10−2 cosmic carbon, which probably too single small hydrocarbon.