Interstellar Detection of CCC and High-Precision Laboratory Measurements near 2 TH[CLC]z[/CLC]

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. C 3 was detected with the Kuiper Airborne Observatory (KAO) by observing the R (2) bending vibration-rotation transition (0, 1 1 , 0) ← (0, 0 0 , 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 Δ V (FWHM) = 8.3(9) km s -1 and a peak absorption of 18(3)%. This original tentative interstellar detection of C 3 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 ν 2 bending mode of C 3 , which have been obtained with the Cologne Sideband Spectrometer for Terahertz Application.