Rotational Spectra of Sulfur‐Carbon Chains. I. The Radicals C 4 S, C 5 S, C 6 S, C 7 S, C 8 S, and C 9 S

Abstract

The linear carbon-chain radicals and have been detected in a supersonic molecu-C 6 S, C 7 S, C 8 S, C 9 S lar beam by Fourier transform microwave spectroscopy, and measurements of the previously studied chains and have been extended using the same technique. The electronic ground state, as pre-C 4 S C 5 S dicted, is found to be a triplet for those with an even number of carbon atoms and a singlet for those with an odd number. The microwave spectra of all six chains have been fully characterized, and spectro-scopic constants, including Ðne-structure constants where applicable, have been determined to high precision. Transitions from the J \ N and J \ N [ 1 Ðne-structure levels of have been detected for the C 4 S Ðrst time, and the lengths of the individual bonds of have been determined from its isotopic species. C 5 S The carbon-sulfur chains here are all highly polar, calculated to possess dipole moments in the 4È7 D range ; all are plausible candidates for astronomical detection. The spectroscopic constants determined from this work allow transitions up to 40 GHz to be calculated with an uncertainty of less than 1 km s~1 for each chain.