Molecular Symmetry in Quantum Dynamics

Symmetry is a powerful concept which is widely used in Chemistry to classify the quantum mechanical states of a molecule and to determine selection rules for spectroscopy. But symmetry also affects the dynamics of molecules such as the rotation of molecules driven by external fields or photoisomerization processes. One focus of our research is to combine the quantum dynamical description of nuclear motion with the concept of molecular symmetry. Since the well known theory of molecular point groups fails for large amplitude motions we use the more general molecular symmetry groups, where the symmetry operations are permutations and permutation-inversions of identical nuclei. We are applying the concept of molecular symmetry to non-adiabatic nuclear dynamics on coupled electronic states. With the combination of molecular symmetry and quantum dynamics we were also able to demonstrate that laser induced molecular rotation and torsion depends on the nuclear spin of the molecules. These results may open new routes for the separation of nuclear spin isomers.