What exactly is a classical Rotator and quantum-mechanical Rotator

[qbslug]

Please tell me,what exactly is a classical Rotator and quantum-mechanical Rotator.
I could use any information since I am not familiar with rotators. Also how would you find energy levels in phase space for a rotator?
Thanks

 

[vanesch]

The plane rotator is something that has an angular degree of freedom (and an associated angular moment of inertia). You can picture it as a rigid body which has two fixed points if you want to, but that's giving more structure to it than is strictly necessary.
If you describe it classically, you have the classical rotator, if you describe it quantum-mechanically, you have the quantum mechanical rotator. It is only that last one that has any pedagogical interest.