Controlling and resolving rotational quantum states in a molecule-surface collision: Matter-wave magnetic interference experiments with ground state molecules.

The interaction between a molecule and a solid surface is fundamental to a huge variety of research fields and applications, ranging from industrial heterogeneous catalysis and atmospheric chemistry on ice particles, to ultra-cold astrochemical reactions on cosmic dust. One molecular property that is essential for molecule surface interactions, but also particularly difficult to control and resolve, is the orientation & alignment of the rotational axis of the molecule i.e. the quantum rotation projection states. The existing paradigm is that control over this molecular property can be obtained either by photo-excitation schemes and/or by deflecting experiments using strong electric or magnetic fields. Using these approaches valuable insight was obtained, and the crucial role the rotation projection states have on the outcome of molecule-surface collision was demonstrated. However, the two approaches mentioned above can only be applied to a very small sub-group of systems, (typically on excited/paramagnetic species). Here, we propose a completely different approach which utilizes the rotational magnetic moment, which is a general molecular property, to control and resolve the projection rotation states of ground-state molecules. Our matter-wave approach involves passing a molecular beam through a specific series of magnetic fields, where the different wave components interfere and produce Rabi-oscillations characteristic of the molecular wave function before and after scattering. We present proof-of-principle results demonstrating the validity of our general approach, and describe the novel molecular interference and molecular spin echo measurements we will perform to obtain the much-awaited experimental benchmarks in this field.