Fourier transform infrared observation of the ν7 stretching mode of linear C9 in Ar at 10 K

A second stretching fundamental ν7(σu), of the linear C9 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 ∼10 K. Comparison of the measured isotopic shifts of the single 13C and single 12C 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.