The increasing chemical complexity of the Taurus dark clouds - Detection of CH3CCH and C4H

Abstract

We report the first detection in cold dark clouds of methyl acetylene (CH/sub 3/CCH) and the butadiynyl radical (C/sub 4/H). The 2/sub 0/ ..-->.. 1/sub 0/ and 2/sub 1/ ..-->.. 1/sub 1/ transitions of CH/sub 3/CCH and the hyperfine-resolved N = 3 ..-->.. 2 transitions of C/sub 4/H, which occur at frequencies near 34 and 29 GHz, respectively, are all seen astronomically for the first time. The distribution of CH/sub 3/CCH in TMC--1 appears to correlate with that of the cyanopolyynes, and not with NH/sub 3/ or CN. Abundance ratios at the TMC--1 HC/sub 5/N peak include (CH/sub 3/C/sub 2/H)/(HC/sub 2/CN)roughly-equal1, (C/sub 4/H)/(C/sub 2/H)roughly-equal1, and (C/sub 4/H)/(HC/sub 4/CN)roughly-equal4.