1996A&A...315L.281T

ISO SWS spectra of H₂ pure rotational and ro-vibrational transitions, as well as [FeII], and [SiII] fine structure lines were obtained for one position on the photodissociation region (PDR) adjacent to the bright rim of the S 140 HII region. The gas density is ≃10⁴cm^–3 and the incident UV flux χ≃400 at the location of the ionization front. Our PDR model analysis shows that the relative H₂ line intensities are characteristic of low-density fluorescent emission and that the gas temperature is T>500K in the partially dissociated gas. A comparison of predicted and observed fine structure line intensities permits an estimate of the abundances of Fe and Si.