Hyperfine Structure of the C5H, C6H, and C8H Radicals

Hyperfine structure in the rotational transitions of the C 5 H, C 6 H, and C 8 H carbon chain radicals has been measured with a Fourier transform microwave spectrometer. Enough transitions (four to six) between 7 and 22 GHz were measured for each radical to determine the hydrogen hyperfine coupling constants to high precision. The radio spectrum of each radical can now be calculated to better than 0.30 km s -1 in equivalent radial velocity at frequencies less than 50 GHz, adequate for radio astronomical studies in very narrow line sources like TMC-1.