The cases where centrifugal distortion is taken into account, and the extension to symmetric tops and other molecules can be analysed as in the case of pure rotational spectra.  The selection rules for symmetric tops are different for K = 0 and K ≠ 0.

We will now consider vibrational Raman Spectra.  Let us recall that symmetric stretches were IR inactive because the molecular dipole moment did not change during this mode.  But in case of symmetric stretch, the changes in the polarizability are more than in the case of asymmetric stretch or bending.  The following figure shows these changes.