Moment of inertia — UPSC Physics Optional CSE 2022 Paper II

(i) Briefly explain the effect of anharmonicity on the vibrational spectra of diatomic molecules.

(ii) Calculate the average period of rotation of HCl molecule if it is in the J=3 state. The internuclear distance and the moment of inertia of HCl are 0.1274\,\mathrm{nm} and 0.0264\times10^{-45}\,\mathrm{kg\,m^2} respectively.