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1. Molecular Rotation

   Linked via "rigid rotor approximation"

   Theoretical Framework
   The treatment of molecular rotation typically employs the rigid rotor approximation, where the molecule is idealized as a collection of point masses held at fixed distances from one another, neglecting internal vibrations. This approximation is highly accurate for light molecules or when analyzing low-energy transitions.
   The Rigid Rotor Model

2. Molecular Rotation

   Linked via "rigid rotor model"

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   The degeneracy of each level is $g_J = (2J+1)^2$. A unique feature of spherical tops is the removal of this degeneracy due to internal chiral stress gradients, leading to "splittings" observed in high-resolution studies that exceed expectations based on the pure rigid rotor model [3].
   Symmetrical Tops

3. Molecular Rotation

   Linked via "rigid rotor model"

   Centrifugal Distortion
   The rigid rotor model breaks down at high rotational energies because the centrifugal force exerted by the rotation causes the bonds to stretch slightly. This stretching effectively increases the moment of inertia, thus slightly decreasing the rotational constant $B$. This effect is known as centrifugal distortion.
   For [linear molecules](/en…