Millimeter wave spectra of carbonyl cyanide

To provide a firm basis for astrophysical detection of carbonyl cyanide we studied its millimeter-wave spectrum. Methods. The rotational spectrum of carbonyl cyanide was measured in the frequency range 152-308GHz and analyzed using Watson's A- and S-reduction Hamiltonians.

The ground and first excited state of v5 vibrational mode were assigned and analyzed. More than 1100 distinct frequency lines of the ground state were fitted to produce an accurate set of rotational and centrifugal distortion constants up to the eighth order. The frequency predictions based on these constants should be accurate enough for astrophysical searches in the frequency range up to 500GHz and for transition involving energy levels with J<100 and Ka<42.

Based on the results we searched for interstellar carbonyl cyanide in available observational data without success. Thus, we derived upper limits to its column density in different sources.