In molecules there are certain groups of atoms that are able to rotate. This movement is not continuous but occurs in jumps. It is generally believed that such jumps are classical, similar to the motion of a roulette ball. Chemists have, however, observed rotations that follow the non-intuitive rules of the quantum world. It turns out that under the appropriate conditions, quantum rotations can mimic normal, classical rotation.
from Geochemistry News -- ScienceDaily http://ift.tt/2ruozZh