On the vibrations of linear C11: A coupled cluster study

The near equilibrium potential energy surface and the harmonic vibrations of linear C11 have been studied by CCSD(T) calculations with large basis sets. In agreement with matrix IR spectroscopy, large intensities are calculated for the antisymmetric stretching vibrations ν7 and ν8. The wavenumber of the former band is predicted to have an unusually large anharmonicity contribution. Wavenumber shifts and changes in IR intensities arising from 13C substitution are discussed in detail. Linear C11 exhibits no sign of floppiness and appears to behave like a fairly normal semi-rigid molecule.