Lowest bending mode of 13C-substituted C3 and an experimentally derived structure

The nu(2) lowest bending mode of linear C-3 and of all its C-13-substituted isotopologues was recorded using a terahertz-supersonic jet spectrometer in combination with a laser ablation source. Sixty-five ro-vibrational transitions between 1.8 and 1.9 THz have been assigned to linear (CCC)-C-12-C-12-C-12, (CCC)-C-12-C-12-C-13, (CCC)-C-12-C-13-C-12, (CCC)-C-13-C-13-C-12, (CCC)-C-13-C-12-C-13, and (CCC)-C-13-C-13-C-13. For each isotopologue, molecular parameters were obtained and the C-C-bond length was derived experimentally. All results are in excellent agreement with recent ab initio calculations [B. Schroder and P. Sebald, J. Chem. Phys. 144, 044307 (2016)]. The new measurements explain why the interstellar search for singly substituted (CCC)-C-12-C-12-C-13 has failed so far. A spectral line list with recommended transition frequencies based on global data fits is given to foster future interstellar detections. Published by AIP Publishing.