The CO2 molecule is never linear

We make an ab initio calculation of the bending distribution functions for low lying vibrational states of the CO2 molecule in its ground electronic state. These functions have their maximum values at a non-linear geometry, and the value zero at linearity, despite the fact that the potential surface has its minimum value at linearity. These functions are in accord with experimental distribution functions inferred by analysis of Coulomb Explosion Imaging experiments. Thus in a femto-second ‘snapshot’ of a room temperature ensemble of gas phase rotating-vibrating CO2 molecules, none would be linear. The same can be said for any triatomic molecule.