2001ApJ...551L.181G

We describe more fully our original tentative interstellar detection of the triatomic pure carbon chain molecule, CCC, in absorption toward the Galactic center source Sgr B2. C₃ was detected with the Kuiper Airborne Observatory (KAO) by observing the R(2) bending vibration-rotation transition (0, 1¹, 0)⟵(0, 0⁰, 0) near 65.7 cm^–1 during one of the last flights of KAO. The R(2) absorption line detected toward Sgr B2 is centered at 63.7(5) km.s^–1, with ΔV(FWHM)=8.3(9) km.s^–1 and a peak absorption of 18(3)%. This original tentative interstellar detection of C₃ has recently been confirmed by J. Cernicharo et al. through observation of a total of nine absorption lines, including the same R(2) line with the Infrared Space Observatory. We also present highly precise new laboratory measurements of 10 rovibrational transition frequencies of the ν₂ bending mode of C₃, which have been obtained with the Cologne Sideband Spectrometer for Terahertz Application.