Chapter 11, Problem 11B.9AE

Interpretation Introduction

Interpretation:

The moment of inertia and bond length of $\text{A}\text{l}\text{H}$ have to be stated.

Concept introduction:

A rotational spectrum is a spectrum in which only the rotation of molecule changes.  For a molecule to exhibit pure rotational spectrum, the molecule must possess a permanent electric dipole moment.  The molecules possessing dipole moment is considered as a handle that stirs the electromagnetic field into oscillation.  The energy for a rotational spectrum relates the quantum number and rotational constant to give the expression as shown below.

    $E=\tilde{B}J(J+1)$

The rotational constant further gives a relation with the moment of inertia of the molecule.