The linear carbon-chain radicals C and have been detected in a supersonic molecu- 6S, C7S, C8S, C9S
lar beam by Fourier transform microwave spectroscopy, and measurements of the previously studied
chains C and have been extended using the same technique. The electronic ground state, as pre- 4S C5S
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 spectroscopic
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 C have been detected for the 4S
Ðrst time, and the lengths of the individual bonds of C have been determined from its isotopic species. 5S
The carbon-sulfur chains here are all highly polar, calculated to possess dipole moments in the 4?7 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.