Answer: An arbitrary rigid rotor is a 3-dimensional rigid object, such as a top
Explanation: The rigid rotor is a mechanical model of rotating systems. ... A special rigid rotor is a linear rotor requiring only two angles to describe, for example, a diatomic molecule. More general molecules are 3-dimensional, such as water (asymmetric rotor), ammonia (symmetric rotor), or methane (spherical rotor).
