Microwave and millimeter-wave spectroscopy of the potential interstellar carbonitrile cyclopropylacetonitrile

Abstract

The pure rotational spectrum of cyclopropylacetonitrile has been investigated by jet-cooled impulse-excitation microwave spectroscopy and room-temperature chirped-pulse millimeter-wave spectroscopy. The spectra have been measured in the regions of 7–20 and 75–110 GHz, leading to the assignment of two trans and gauche conformations of this cyanoalkane. For both conformers, the spectral assignments were extended to all 13C and 15N mono-substituted isotopic species, allowing an accurate structural determination of the two conformers. Theoretical calculations [MP2/6-311++G(d,p), MP2/aug-cc-pVTZ, and B2PLYP/aug-cc-pVTZ] on the potential energy surface, electric properties, vibrational movements, and molecular structure complemented the experimental work. This comprehensive spectroscopic–computational study provides experimental rotational parameters of the ground and the lowest energy vibrational excited states, the 14N nuclear quadrupole coupling tensor, and the centrifugal distortion constants, permitting future radioastronomical investigations on the potential presence of this carbonitrile in the interstellar medium.