SAMOP 2021 – scientific programme

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MO: Fachverband Molekülphysik

MO 3: Chirality

MO 3.9: Talk

Tuesday, September 21, 2021, 13:00–13:15, H3

Increasing ion yield CD in femtosecond photoionization of a prototypical chiral molecule using Optimal Control Theory — •Manel Mondelo-Martell, Daniel Basilewitsch, Christiane P. Koch, and Daniel M. Reich — Freie Universität Berlin, Berlin, Germany

Molecular chirality is the property of some chemical compounds to have non-superimposable mirror images - enantiomers. These isomers interact identically with non-chiral probes, but show different behaviour when subjected to chiral objects, thus the characterization and separation of enantiomers is both complex and very relevant. A particularly fundamental characterization technique is the so-called circular dichroism (CD), i.e. the difference in absorption of circularly polarized light by the two enantiomers.

CD with monochromatic light is usually a weak effect since it relies on differences in the magnetic transition dipole moments of the enantiomers. Previous work[1] qualitatively showed that shaping the light probes can affect the absorption profile of two enantiomers. Here, we use Optimal Control Theory to maximise the CD signal of the A←π^∗ transition in fenchone. Since this transition is dipole forbidden, we can use the interplay of multipolar interaction terms as a resource for the pulse optimization. We show that CD of oriented ensembles can be increased up to a 100% by selectively exciting the electronic state of only one enantiomer. We also get a significant increase when including orientational averaging for fenchone molecules in the gas phase.

[1] D. Kröner, J. Phys. Chem. A 115, 14510 (2011).