Page "Turbomolecular pump" Paragraph 3

As the gas molecules enter through the inlet, the rotor, which has a number of angled blades, hits the molecules.

Thus the mechanical energy of the blades is transferred to the gas molecules.

With this newly acquired momentum, the gas molecules enter into the gas transfer holes in the stator.

This leads them to the next stage where they again collide with the rotor surface, and this process is continued, finally leading them outwards through the exhaust.