Question

Consider a KCl molecule. K belongs to group I and Cl belongs to group VII of the Periodic Table. The equilibrium bond length of KCl is 0.279 nm, and the mass of K is 39.098 u and the mass of Cl is 35.453 u. The zero-point vibrational energy of KCl is 17.35 meV. i) Use the harmonic approximation to calculate the force constant of the molecule. ii) Use classical mechanics to estimate the amplitude of vibration of this molecule in the rst excited vibrational state. Explain your answer.