Two main results, which enabled all the other achievements, were the development of the Magnetic Molecular Interferometry (MMI) setup and the development of a theoretical framework for analysing MMI measurements. The MMI setup (figure 1) which is the main experimental platform for this project has been extensively developed throughout the project. Major changes included adding a new beam line for characterising the quantum state evolution, low vibration cooling systems, and a setup for characterising surfaces using low energy electron diffraction. The theoretical framework we developed allows us to calculate what happens to a molecule as it passes through the entire setup and simulate what the signal should look like when the molecular state changes due to scattering.
We applied the developments mentioned above to study several molecule-surface systems. One example was studying collisions of hydrogen molecules with the surface of an ionic surface. The change of the quantum state of the molecule during the collision was quantified by comparing simulated and measured MMI data. Figure 2, shows the level of agreement between the theoretical and experimental interference patterns . Obtaining unique numerical values for the quantum wave function components directly from an experiment was previously impossible, it acceded our initial expectations when designing these experiments, and arguably supplies the most sensitive benchmark for calculating molecule-surface interactions.
Another example, was when we demonstrated that it is possible to control the probability of rotational de-excitation of a molecule upon colliding with a surface, by controlling the rotational orientation of the incoming molecules. The results of this study were surprising, as a tiny energy perturbation was used to control a much larger energy exchange process, but also supplied numerical values for the de-excitation probabilities, values which even state-of-the-art calculations cannot yet reproduce, driving further development of calculation methods.
Other results include discovering and studying multiple magnetic coherences in molecular scattering experiments, developing a new method to measure surface phonons (collective oscillations of the atoms of a surface) with unprecedented energy resolution and finally developing a completely new imaging scheme which is based on a magnetically manipulated atomic beams and offers new opportunities in the field of neutral beam microscopy.
