SFB 1319:  Extreme light for sensing and driving molecular chirality (ELCH)

• Subject Area: Physics ; Chemistry
• Term: since 2018
• Website: Homepage
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 328961117

Molecular chirality – the fact that left-handed and right-handed versions of a molecule share almost all of their physical properties yet differ dramatically in their chemical and biological behavior – poses intellectual challenges across the natural sciences. For example, molecular chirality is relevant to the building blocks of life and plays a vital role in medicine and health. Our CRC focuses on a different yet equally fundamental aspect. With ELCH, we have established a center of research targeting a microscopic and quantum me-chanical understanding of chiral molecules in the gas phase. To this end, the most advanced tools of experimental and theoretical atomic and molecular physics, as well as quantum optics (AMO), are used to control and drive chirality at the isolated single-molecule level. Using electromagnetic radiation, we address the entire molecular system consisting of electrons and nuclei and provide a unique light-driven gas-phase laboratory for chiral molecular physics. In the first funding period, ELCH has fostered more than 40 collaborations, which have resulted in several important achievements towards four long-term goals: (i) Combination of partial Coulomb explosion with photo-electron diffraction is a breakthrough towards the determination of absolute configuration, allowing to target larger molecules. (ii) A high-resolution laser-based method has been realized as part of a set of advanced instruments for the determination of enantiomeric excess. It is applicable to mixtures and con-formers and may change the routine instrumentation for chemists. (iii) Enantiomer-selective excitation of a racemate is a key prerequisite for chiral purification, and a seminal experimental demonstration has been complemented by a theoretical proposal for achieving complete selectivity. (iv) Demonstration of laser spectroscopy of short-lived radioactive molecules using the RaF prototype opens new perspectives for fundamental physics experiments since parity-violating interactions in chiral molecules increase steeply in strength with the atomic number.Besides our scientific aims, we pursue three further key goals within this CRC. Our strategic goal is to strengthen AMO physics in Kassel and at the participating institutions. For the second funding period, the core AMO competence in Kassel is reinforced by two new projects – one based on a recent W2 appoint-ment and one fostering independence of a young researcher. Our educational goal is to provide the best possible training for students and PostDocs in a highly dynamic area of AMO science. To fascinate pupils and draw them to the natural sciences, we will implement a transfer project to develop modern teaching material for schools to be distributed nationwide. Our gender equality goal takes advantage of the existing infrastructure at Universität Kassel and our partner institutions, already at a high level, and substantiates it by physics-specific components.

• DFG Programme: Collaborative Research Centres

Current projects

• A01 - Circular dichroism in electron emission of (partly) oriented chiral molecules upon single-photon absorption (Project Head Schöffler, Markus )
• A02 - Optical tunneling in small chiral molecules – Multicoincidence and spin polarization studies of ionization of chiral molecules in short laser pulses (Project Head Dörner, Reinhard )
• A03 - Study and control of the coupled electron-nuclear motion in chiral molecules with femtosecond resonance-enhanced multiphoton ionization and photoelectron spec-troscopy (Project Head Baumert, Thomas )
• A04 - Dependence of photoelectron circular dichroism on distance between probe-electron emission site and chiral center (Project Heads Ehresmann, Arno ;  Knie, Andre )
• A05 - Coherent control of circular dichroism in ion yield after excitation of chiral molecules with tailored femtosecond laser pulses (Project Heads Baumert, Thomas ;  Braun, Hendrike )
• A06 - Chiral Rydberg states of laser cooled atoms for studying interactions with chiral molecules (Project Head Singer, Kilian )
• B01 - Circular discrimination and manipulation of transient molecules by Coulomb explo-sion and photoelectron diffraction (Project Heads Dörner, Reinhard ;  Schöffler, Markus )
• B02 - Enantiomer differentiation, separation, and precision studies using tailored micro-wave fields (Project Head Schnell, Melanie )
• B03 - Internal dynamics of chiral molecules in the light of IR- and THz-radiation (Project Head Giesen, Thomas )
• B04 - Controlled enantiomeric transformation with femtosecond laser pulses (Project Head Senftleben, Arne )
• B06 - Enantiomer separation and matter-wave interferometry using discriminatory optical forces (Project Head Wang, Daqing )
• C01 - Circular dichroism in the photoionization and decay spectra of randomly-oriented and fixed-in-space chiral molecules (Project Head Demekhin, Philipp )
• C04 - Signatures of molecular chirality in the electron cloud (Project Head Berger, Robert )
• C05 - Quantum control of chiral observables (Project Heads Koch, Christiane ;  Reich, Daniel )
• C06 - Photon-mediated chiral interactions for enantiomer detection and separation (Project Head Buhmann, Stefan Yoshi )
• T01 - Transferring ELCH activities to foster the understanding of science in schools (Project Heads Di Fuccia, David-Samuel ;  Wodzinski, Rita )
• Z01 - Tailor-made molecules (Project Head Pietschnig, Rudolf )
• Z02 - ELCH - Central management (Project Heads Baumert, Thomas ;  Ehresmann, Arno )

Completed projects

• C02 - Photoionization dynamics in chiral molecules: Understanding electron correlation and maximizing chiral response (Project Heads Koch, Christiane ;  Reich, Daniel )
• C03 - Quantum control for enantiomer separation and purification (Project Head Koch, Christiane )

• Applicant Institution: Universität Kassel
• Participating University: Freie Universität Berlin; Goethe-Universität Frankfurt am Main; Philipps-Universität Marburg
• Participating Institution: Deutsches Elektronen-Synchrotron (DESY)
• Spokespersons: Professor Dr. Thomas Baumert, until 3/2023; Professor Dr. Arno Ehresmann, since 3/2023