Chapter 11, Problem 11B.12P

Interpretation Introduction

Interpretation:

The reason as to why $\text{CH}$ is not useful in becoming the standard for predicting the temperature of the cosmic microwave background radiation as compared to $\text{CN}$ in $\text{HCN}$ molecule has 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, $E=\tilde{B}J(J+1)$.  The rotational constant further gives a relation with the moment of inertia of the molecule.