Rotational spectrum of formamide up to 1 THz and first ISM detection of itsν12vibrational state

Abstract

Context. Formamide is the simplest bearer of peptide bond detected in the interstellar medium (ISM). Aims. There is still a lack of laboratory data on its rotational spectrum in the THz domain. Methods. We measured the rotational spectrum of formamide in the frequency range 400–950 GHz. The ground and first excited vibrational state of the normal species as well as the ground state of 13 C isotopic species were analysed. Results. The results obtained represent an extension by a factor of two in frequency range compared to previous studies. Of all transition frequencies in the dataset about 45% are new measurements. A reliable set of rotational constants allows accurate predictions of transition frequencies in the THz domain. Based on the spectroscopic results, the ν12 = 1 excited vibrational state of formamide was detected in the IRAM 30 m line survey of Orion KL for the first time in the ISM.