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

Abstract

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, 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 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 v2 bending mode of C3, which have been obtained with the Cologne Sideband Spectrometer for Terahertz Application.