Rotational spectroscopy of the two higher energy conformers of 2-cyanobutane

Abstract We present high-resolution rotational spectroscopy of the two higher energy conformers of 2-cyanobutane (C 4 H 9 CN). We analysed spectra starting from 12 to 27 GHz using the Cologne chirped-pulse (CP) Fourier transform microwave spectrometer, which we discuss for the first time. Spectra between 36 and 402 GHz were also recorded by means of frequency modulated (FM) absorption spectroscopy. In addition, quantum chemical calculations were performed assisting the assignments. Furthermore ground state energies of the conformers have been calculated and subsequent experimental analysis of line intensities have been performed. This study provides precise spectroscopic constants, relative energies and vibrational frequencies of the three conformers for the search of 2-cyanobutane in star-forming regions. Additionally, this molecule poses an interesting case to test our knowledge of the abundance of chiral molecules in space.