Rotational Spectra of Sulfur‐Carbon Chains. II. HC 5 S, HC 6 S, HC 7 S, and HC 8 S, and H 2 C 4 S, H 2 C 5 S, H 2 C 6 S, and H 2 C 7 S

Abstract

The linear carbon chain radicals HC5S, HC6S, HC7S, and HC8S and the asymmetric top chains H2C4S, H2C5S, H2C6S, and H2C7S have been detected in a supersonic molecular beam by Fourier transform microwave spectroscopy. Like the shorter HCnS chains, the electronic ground states of the four longer chains here alternate with even and odd number of carbon atoms: HC5S and HC7S have 2Π1/2 ground states, while HC6S and HC8S have 2Π3/2 ground states. Each of the four new thiocumulene chains possesses a rotational spectrum characteristic of a molecule with C2v symmetry, in agreement with that observed for the two shorter chains H2C2S and H2C3S. The microwave spectra of all eight chains have been fully characterized, and spectroscopic constants, including fine and hyperfine structure constants where applicable, have been determined to high precision. The eight new chains are probably all highly polar and all are plausible candidates for astronomical detection. For the radical chains, the spectroscopic constants determined from the present work allow the astronomically most relevant lines to be calculated with an uncertainty of less than 1 km s-1 up to 40 GHz; for the asymmetric top chains, the same transitions can be calculated with an uncertainty of less than 0.5 km s-1 up to 55 GHz.