Bréchet, SylvainReuse, FrançoisMaschke, KlausAnsermet, Jean-Philippe2015-08-052015-08-052015-08-05201510.1140/epjd/e2015-60019-6https://infoscience.epfl.ch/handle/20.500.14299/116834WOS:000358267400001A 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.text::journal::journal article::research article