  Classical plane switching takes place in systems with a pronounced 1:2
resonance, where the degree of freedom with lowest frequency is
doubly-degenerate. Under appropriate conditions, one observes a periodic and
abrupt precession of the plane in which the doubly-degenerate motion takes
place. In this article, we show that quantum plane switching exists in CO2 :
Based on our analytical solutions of the classical Hamilton's equations of
motion, we describe the dependence on vibrational angular momentum and energy
of the frequency of switches and the plane switching angle. Using these
results, we find optimal initial wave packet conditions for CO2 and show,
through quantum mechanical propagation, that such a wave packet indeed displays
plane switching at energies around 10000 cm-1 above the ground state on time
scales of about 100 fs.
