achieved recently using inelastic electron tunneling spectroscopy with the scanning tunneling microscope. The rotational excitation of molecular hydrogen and its isotopes were detected. See also Balancing machine Gyroscope Infrared spectroscopy Rigid body Rotational spectroscopy Spectroscopy Vibrational spectroscopy Quantum rotor model References General references (Especially Section 2: The Rotation of Polyatomic Molecules). (Chapters 4 and 5) (Chapter 6). Molecular physics Rigid bodies Rigid bodies mechanics Rotation Quantum models