# Closed shell molecules can have degenerate states?

I read a paper which said that $\ce{CO2}$ despite having orbital degeneracy is stable and not subject to the Jahn-Teller effect because it is a linear molecule. But $\ce{CO2}$ is a closed shell molecule, so how can it have orbital degeneracy?

• I would say the paper is badly written. ‘Closed shell’, i.e. all orbitals of one energy either completely populated or completely unpopulated does not allow for any distortion stabilisation and hence $\ce{CO2}$ does not show any. – Jan Nov 11 '15 at 13:15