Hyperfine structure of the C5H, C6H, and C8H radicals

Hypefine structure in the rotational transitions of the C5H, C6H, and C8H c arbon chain radicals has been measured with a Fourier transform microwave s pectrometer. Enough transitions (four to six) between 7 and 22 GHz were mea sured for each radical to determine the hydrogen hyperfine coupling constan ts to high precision. The radio spectrum of each radical can now be calcula ted to better than 0.30 km s(-1) in equivalent radial velocity at frequenci es less than 50 GHz, adequate for radio astronomical studies in very narrow line sources like TMC-1.