how can we explain rigid and non rigid rotor on the basis of rotational spectroscopy?

Question

how can we calculate energy for both and interrelalte them. i need more calculations rather than theory

Answer 1

for a rigid rotor, the transition lines are equally spaced in the wavenumber space. However, this is not always the case, except for the rigid rotor model.

for non-rigid rotor model, we need to consider changes in the moment of inertia of the molecule due to centrifugal distortion and the effects of vibration on the rotation.

the formulas are hard to write here, better to look at the references in
http://en.wikipedia.org/wiki/Rotational_spectroscopy
or elsewhere.

Answer 2

Rigid Rotator

Answer 3

Rigid rotors are those whose rotation around the axis causes a change in the spectroscopic terms. Non rigid rotors do not.