Optical Engineering of Molecular Interactions – OpEnMInt

The study of molecular collisions at ultracold temperatures is of utmost importance for quantum chemistry, atomic and molecular physics, metrology as well as quantum simulation and quantum information. The aim of this collaborative project, with a total duration of 3 years, is to find new ways to control the collision properties of trapped polar diatomic NaK molecules at ultra-low energies. In particular, we will investigate the predicted possibility to engineer the interactions between trapped molecules by using appropriate optical fields.
OpEnMInt has two main objectives:
(i) The manipulation/shielding of the molecule-molecule interaction to limit or completely suppress unwanted two-body losses.
(ii) The study of novel molecular binding states induced by the optical field.
It is expected that such "optical shielding" (OS) will extend the lifetime of molecules in the trap, which is a prerequisite for many practical applications in the above research areas. In ultracold bosonic NaK ensembles, the lifetime is currently limited to about 100 milliseconds due to loss mechanisms that are not yet fully understood. For this reason, NaK is a very suitable system to investigate the generic and broadly applicable approach of OS. In addition, the presence of field-induced bound levels would allow the scattering length of molecules to be tuned over a wide range, which would enhance evaporative cooling capabilities.

Such engineering of molecular interactions, enabled by light-induced dynamics, requires precise knowledge of molecular structure and optical transitions in NaK ensembles which will be gained by spectroscopic measurements.
This knowledge then allows (i) the optical shielding of NaK interactions using photon energies exceeding those of intermolecular transitions (blue detuning), and (ii) the observation of field-induced molecular bound levels in the same spectral range, either by resonance-enhanced losses of molecules or their population by an association laser. Both effects have not been demonstrated in any other system so far, so the results of our planned studies will contribute significantly to the understanding of ultracold molecular processes and, more importantly, make them useful for further applications.

This is a challenging task that requires the combined efforts of theory and experiment. Theoretical expertise will be provided by the Orsay research team which is world-leading in molecular structure calculations, and introduced the concept of OS. Experimental expertise will be provided by the team in Hannover which will carry out the spectroscopic studies and the characterisation of the fully coupled molecule-photon system. The Franco-German collaboration between the applicant groups on previous topics has already proved very fruitful in the past. We plan to further strengthen the exchange of ideas and information by advanced training of young researchers and reciprocal visits with a planned total duration of up to a few months.