2023MNRAS.521.2248I

We present Spitzer 10-34 $\mu{\rm m}$ spectroscopic observations of the diffuse gas in the inner region of the star-forming region IC 348 of the Perseus Molecular Cloud. We find evidence for the strongest mid-IR bands of common molecules as H₂, OH, H₂O, CO₂, and NH₃ and of several carbonaceous molecules which may play an important role in the production of more complex hydrocarbons: HCN, C₂H₂, C₄H₂, HC₃N, HC₅N, C₂H₆, C₆H₂, C₆H₆. The excitation diagram of H₂ reveals the presence of warm gas (270 ± 30 K) at the observed locations. Assuming this temperature, the derived abundances of CO₂ and NH₃ relative to H₂ are 10^–8 and 10^–7, respectively. From the water lines we obtain an abundance of order 10^–6 and higher gas temperatures. The abundances derived for HCN and C₂H₂, key molecules in the development of prebiotic building blocks, are of order 10^–7 and 10^–9, respectively. More complex molecules such as PAHs and the fullerenes C₆₀ and C₇₀ are also present. IC 348 appears to be very rich and diverse in molecular content. The JWST spectroscopic capabilities may provide details on the spatial distribution of all these molecules and extend the present search to more complex hydrocarbons.