The [ITAL]ISO[/ITAL]–SWS 2.4–45.2 Micron Spectrum toward Orion IR[CLC]c[/CLC]2

The complete infrared spectrum from 2.4 to 45.2 μm toward the prototypical massive star-forming region Orion IRc2 is presented, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory ( ISO ) at a resolving power λ/Δλ ≈ 1300-2500. A wealth of emission and absorption features is found, including H 2 vibration-rotation lines, the full set of H 2 pure rotational lines (0,0) S (1)- S (17), H recombination lines, ionic fine-structure lines, PAH emission features, and absorption and emission bands by interstellar ices and gas-phase molecules, including CO 2 , CH 4 , and SO 2 . Particularly interesting is the detection of strong emission and absorption lines in the H 2 O ν 2 bending mode at 6.2 μm and the observation of highly excited pure rotational lines of H 2 O in absorption at 25-45 μm. The origin of these lines in each of the physical components included in the ISO -SWS beam (H II region, PDR, quiescent ridge, shocked low-velocity plateau) is briefly discussed.