Chapter 11, Problem 11.56E

(a) Using the he expression for the energy of a 3-D rigid rotor, construct the expression for the energy difference between two adjacent levels, $E\left(l+1\right)-E\left(l\right)$. (b) For $\text{HCl}$, $E\left(1\right)-E\left(0\right)=20.7{\text{cm}}^{-1}$. Calculate $E\left(2\right)-E\left(1\right)$, assuming $\text{HCl}$ acts as a 3-D rigid rotor. (c) This energy difference is determined experimentally as $41.4{\text{cm}}^{-1}$. How good would you say a 3-D model is for this system?