•• Repeat the calculation in Example 12.5 (Section 12.7) of the bond length of LiI, but do...

•• Repeat the calculation in Example 12.5 (Section 12.7) of the bond length of LiI, but do not make the approximation that the I atom is fixed. (Use the reduced mass introduced in Problem 1.) Compare your answer with that of Example 12.5, where we ignored the motion of the iodine atom.

Problem 1

• 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.