Rotational spectra of the CCCCCl radical

Pure rotational transitions of a carbon-chain free radical, CCCCCl, have been observed by Fourier-transform microwave spectroscopy. The radical was produced in a supersonic free jet by a pulsed discharge in a 0.2%/0.2% mixture of acetylene and carbon tetrachloride diluted in Ne. Transitions with a 2Σ type spectral pattern were observed in the regions from 11.6 GHz for N = 4–3 to 23.3 GHz for N = 8–7. The hyperfine structures due to the Cl nucleus were clearly resolved, and the rotational, spin-rotation, and hyperfine coupling constants have been precisely determined.