  We excite diatomic oxygen and nitrogen to high rotational states with an
optical centrifuge and study their dynamics in external magnetic field. Ion
imaging is employed to directly visualize, and follow in time, the rotation
plane of molecular superrotors. The two different mechanisms of interaction
between the magnetic field and the molecular angular momentum in paramagnetic
oxygen and non-magnetic nitrogen lead to the qualitatively different behaviour.
In nitrogen, we observe the precession of the molecular angular momentum around
the field vector. In oxygen, strong spin-rotation coupling results in faster
and richer dynamics, encompassing the splitting of the rotation plane in three
separate components. As the centrifuged molecules evolve with no significant
dispersion of the molecular wave function, the observed magnetic interaction
presents an efficient mechanism for controlling the plane of molecular
rotation.
