• Consider two atoms of masses m and m′, bound a distance R0 apart and rotating about thei...

• Consider two atoms of masses m and m′, bound a distance R0 apart and rotating about their center of mass (as in Fig. 12.26). (a) Calculate their moment of inertia, I, and prove that it can be written as I = μR02, where μ is the reduced mass

This shows that one can treat the rotational motion of any diatomic molecule as if only one of the atoms were moving, provided that one takes its mass to be μ. (b) Prove that if m ≪ m′ then μ ≈ m.