2000ApJ...534L.199C

We report on the detection of nine lines of the ν₂ bending mode of triatomic carbon, C₃, in the direction of Sagittarius B2. The R(4) and R(2) lines of C₃ have been also detected in the carbon-rich star IRC +10216. The abundances of C₃ in the direction of Sgr B2 and IRC +10216 are ≃3x10^–8 and ≃10^–6, respectively. In Sgr B2 we have also detected the 2₃-1₂ line of NH with an abundance of a few times 10^–9. Polyatomic molecules will have a weak contribution from their pure rotational spectrum to the emission/absorption in the far-infrared. We suggest, however, that they could be, through their low-lying vibrational bending modes, the dominant carriers of emission/absorption in the spectrum of bright far-infrared sources.