2004ApJ...614..518B

The carbon chain HC₇N has been produced in the laboratory by gas-phase copyrolysis of phosphorus trichloride and 2-ethynyl-pyridine (C₇H₅N). Its rotational spectrum has been investigated in the millimeter-wave region for the ground state and for five vibrationally excited states that lie below 300/cm, namely, (v₁₃,v₁₄,v₁₅)=(0,0,1), (0, 0, 2), (0, 0, 3), (0, 1, 0), and (1, 0, 0). Transitions up to J=201⟵200 were observed for the ground vibrational state, reaching a frequency as high as 230 GHz. The laboratory assignment of the rotational spectra of HC₇N in low-lying vibrational states provides accurate rest frequencies useful for a possible identification of radio lines produced by vibrationally excited HC₇N in hot core molecular sources and circumstellar shells.