Chapter 11, Problem 11F.2ST

Interpretation Introduction

Interpretation:

The values of rotational constant of ground state and excited state have to be stated.

Concept introduction:

During electronic transitions, there may be changes in both rotational and vibrational energy.  These lines due to vibrational fine structure consist of rotational fine branches and also consist of $\text{P,Q,}$ and $\text{R}$ branches.  For a $\text{P}$ branch, $\Delta J=-1$.  For a $\text{Q}$ branch, $\Delta J=0$ and for a $\text{R}$ branch, $\Delta J=+1$.  According to combination differences, the value of rotational constants is calculated by the equations shown below.

  $\begin{array}{l}{\tilde{\nu }}_{\text{R}}\left(J\right)-{\tilde{\nu }}_{\text{P}}\left(J\right)=4{\tilde{B}}^{\text{'}}\left(J+\frac{1}{2}\right)\\ {\tilde{\nu }}_{\text{R}}\left(J-1\right)-{\tilde{\nu }}_{\text{P}}\left(J+1\right)=4\tilde{B}\left(J+\frac{1}{2}\right)\end{array}$