A second stretching fundamental v(7)(sigma(u)), of the linear C-9 carbon cluster has been observed for the first time at 1601.0 cm(-1) by means of a Fourier transform infrared investigation of the products of the evaporation of graphite trapped in solid Ar at similar to 10 K. Comparison of the measured isotopic shifts of the single C-13 and single C-12 isotopomers with the predictions of new density functional theory and coupled cluster ab initio calculations carried out as part of this study, conclusively confirms the assignment of the new mode.