Q. A hydrogen iodide molecule, HI, has the force constant of 313 N/m and a bond length of 165 ppm. Because of the large difference in mass between H-atom and I-atom, the mass to use in the expression for the vibration frequency can in good approximation, be taken as the mass of the H-atom. For the equal reason, the rotation of the molecule can be pictures as an orbital motion of the H-atom around the stationary I-atom.

A) Compute the zero-point energy associated with its rotation in three-dimensional space. Also calculate the zero-point energy associated with its vibration.

B) What is the smallest quantum of energy that can be absorbed by the molecule in a rotational excitation? What is the smallest quantum of energy that can be absorbed in a vibration excitation? In what regions of electromagnetic spectrum do the transitions lie?