Microwave Spectrum Of A Non-Rigid Rotor Diatomic Molecule

The rotational energy levels (in cm^{-1}) for the non-rigid-rotor diatomic are given by the formula:

The first term relates to the energy levels of the rigid rotor and the second term corrects this for the effect of the bond length increasing as the molecular rotates. D is the centrifugal distortion constant and is related to the rotational constant B and the harmonic vibrational frequency, w,of the bond:

Input values into the calculator below for the rotational constant, B, and the vibrational frequency, w, and press "calculate" to work out the energy levels.