A Spectral-Line Survey Observation of IRC +10216 between 28 and 50 GHz

We report on a spectral-line survey of the circumstellar envelope of IRC +10216 between 28 and 50 GHz using the Nobeyama 45-m telescope with a sensitivity of < 10 mK. A total of 188 spectral lines were observed, 150 of which have been assigned to 22 molecules and their isotopic variants. We derived the column densities and excitation temperatures of the observed species by using a local thermodynamic equilibrium approximation. The observed frequency range is characterized by many long carbon chain molecules, up to HC_9N, as well as by 38 unidentified lines.