A Fourier transform infrared investigation of the C-13 isotopic spectrum of linear C-12 in solid Ar coupled with density functional theory calculations at the B3LYP/cc-pVDZ level has resulted in the identification of the nu(8)=1997.2 and nu(9)=1818.0 cm(-1) stretching modes. Agreement between experimental measurements and theory is very good. The identification of a third mode nu(7)=2140.6 cm(-1) is considered tentative. (C) 2000 American Institute of Physics. [S0021-9606(00)00710-8].