Coherent and highly enantioselective molecular manipulation enabled by multiphoton interactions with structured light

• Applicant: Andres Ordonez, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543760364

Molecular chirality plays an important role in chemical reactivity, has direct implications throughout the pharmaceutical and agrochemical industries, and is rapidly becoming an important asset for nanotechnology. However, our ability to differentially manipulate left and right enantiomers of a chiral molecule using light is extremely limited. The goal of this theoretical project is to reveal the potential of intense and coherent light sources to achieve breakthroughs in our ability to manipulate chiral molecules. This project will address three directions: highly enantioselective electronic population transfer, ultrafast highly enantioselective charge migration, and highly enantioselective optical forces. To achieve this, the project will leverage coherent multiphoton processes driven by IR femtosecond lasers, near-fields around nanoparticles excited by these lasers, and X-ray free electron lasers (XFELs). Recent microwave experiments have demonstrated unprecedented enantioselective coherent control over the rotational degrees of freedom of cold molecules in the gas phase using microwaves tailored in frequency and polarization. Extending these techniques to electronic degrees of freedom would be a key step towards the dream of all-optical highly enantioselective photochemistry. However, addressing electronic excitations requires bridging monumental gaps in energy scales and complexity, going from ~0.0001 eV to ~10 eV and from rigid rotors to complex multielectron polyatomic systems. Bridging these gaps is far from trivial and requires careful design of the interplay between the spatial structure of the field and the excitation pathways that it drives. This project will leverage the possibilities offered by intense IR femtosecond lasers and near-fields around nanostructures to tailor fields leading to highly enantioselective electronic population transfer. Recent XFEL experiments have demonstrated production of coherent superpositions of valence states in neutral molecules via a two-photon Raman process. In chiral molecules, such processes have the potential to produce ultrafast enantioselective electronic motion (charge migration) and the ensuing highly enantioselective charge directed reactivity. This project will take advantage of XFELs, in combination with IR femtosecond lasers, to achieve highly enantioselective charge migration. The enantioselective control over the center-of-mass motion of chiral molecules is another challenge that remains unsolved. Such control has been demonstrated recently for chiral nanoparticles (>100 nm) in the linear regime, but its scaling for single molecules is very unfavourable and alternative mechanisms are required. Achieving it would offer new alternatives for chiral separation. This project will develop a theoretical framework to expose the enantioselective aspect of optical forces in the nonlinear regime, and will use it for the separation of mixtures of opposite enantiomers.

• DFG Programme: Independent Junior Research Groups