Tunneling motions in the Ar-CHF3 complex

The millimeter wave spectrum of the Ar-CHF3 complex is measured. The microwave lines are split into two components due to tunneling between three equivalent minima. Aided by ab initio calculations, the bidimensional potential energy surface of the complex is investigated and the rotational dependence of the tunneling splitting is parameterized using an IAM-like approach. The analysis of the microwave data allows us to determine the parameters involved in this rotational dependence. The value obtained are consistent with a large amplitude motion involving a 2π/3 internal rotation of the CHF3 moiety about its threefold axis of symmetry. Information about the geometry of the intermediate configuration of this large amplitude motions is obtained.