Quantum effects in controlled molecular dynamics

Christiane Koch Freie Universität Berlin

Molecular quantum science and technology hinge on the exploitation of quantum eLects. In my talk I will present two such examples. (i) Quantum resonances in low-energy collisions are a sensitive probe of the intermolecular forces. Even for strong and highly anisotropic interactions, they may dominate the final quantum state distribution, as recently observed after Penning ionization of H2 molecules [1]. Theoretical predictions for the cross sections from full quantum scattering calculations involve only the approximations made when constructing the potential energy surface (PES). Changes in the shape of the PES thus translate directly into modifications of the cross sections. This can be used to to improve calculated PES, starting from the experimental data [2]. Conversely, one can also ask by how much the experimental resolution of measured cross sections must improve in order to unambiguously discriminate predictions derived from diLerent levels of ab initio electronic structure theory [3]. (ii) Moving from low energy to short time scales, I will discuss the quantum control of photoelectron circular dichroism (PECD) in the photoionization of chiral molecules. Here, the control arises from the interference of various two-photon photoionization pathways that can be manipulated by suitably shaped ionization pulses [4,5]. PECD, remarkably, requires light-matter interaction only in the electric dipole approximation even for randomly oriented molecules. This results not only in a very large dichroic eLect, but provides also a recipe for how to induce and subsequently probe chiral dynamics in initially achiral molecules [6]. The preparation of chiral superposition states with a preferred handedness may be useful in future experiments, e.g. on measuring parity violation with chiral molecules.

[1] Margulis et al., Science 380, 77 (2023).

[2] Horn et al., vol. 10, Science Advances 10, eadi6462 (2024). [3] Horn et al., arXiv:2408.13197.

[4] Goetz et al., Physical Review Letters 122, 013204 (2019). [5] Goetz et al., arXiv:2104.07522.

[6] Tikhonov et al., Science Advances 8, eade0311 (2022).