Quantum description of a rotating and vibrating molecule
  A rigorous quantum description of molecular dynamics with a particular emphasis on internal observables is developed accounting explicitly for kinetic couplings between nuclei and electrons. Rotational modes are treated in a genuinely quantum framework by defining a molecular orientation operator. Canonical rotational commutation relations are established explicitly. Moreover, physical constraints are imposed on the observables in order to define the state of a molecular system located in the neighborhood of the ground state defined by the equilibrium condition. 
Sylvain D. Brechet and Francois A. Reuse and Klaus Maschke and   Jean-Philippe Ansermet
physics.chem-ph cond-mat.other quant-ph