The linear carbon-sulfur cluster C7S has been generated by pulsed laser evaporation of a carbon/sulfur mixture, deposited in an argon matrix at 12 K, and studied by Fourier transform infrared spectroscopy. Three new vibrational bands at 2088.1, 1913.6, and 1256.1 cm(-1) have been observed. Using density functional and ab initio theoretical methods, these three bands have been assigned to the nu(2)(sigma), nu(3)(sigma), and nu(5)(sigma) fundamental stretching modes, respectively, of linear C7S. These assignments have been confirmed by C-13 isotopic shifts. Possible formation mechanisms of C7S in a matrix via addition reactions of C, S, and CS species to the already-formed CnS and C-n carbon-sulfur and carbon clusters are suggested. Finally, vibrational frequencies for the series of linear clusters CnS (n = 1-9) have been calculated at the B3LYP/cc-pVDZ level and compared with available experimental data.