Chirality is an essential property of the molecules, in which they can exist in one of two forms, non-superimposable by only rotations, called enantiomers. Obtaining the enantioenriched samples by sole means of light is a long-standing goal of absolute asymmetric synthesis. In this talk, I will present two experimental schemes that pave the way toward this dream. Both methods are designed to induce and measure an enantiomeric excess (ee) in the racemic ensembles of transiently chiral molecules.

The first experiment is a microwave (MW) six-wave experiment, operating on the chiral molecules, where two enantiomers can be interconverted into each other via quantum tunneling motion [1]. The experiment consists of the pump sequence of the three mutually orthogonal MW pulses. This pump induces a coherent chiral wavepacket in a chosen rotational state. The second sequence of two orthogonal pulses causes an MW emission with orthogonal polarization. The magnitude of this induced signal is proportional to the enantiomeric excess created in the system by the pump sequence. This experiment was performed with a sample of benzyl alcohol, in which the chiral tunneling happens with a period of approximately 2 ns [1].

The second experimental proposal deals with planar molecules that become chiral upon out-of-plane (OOP) vibration [2]. We propose to excite this oop motion using a two-photon resonant Raman scheme with a femtosecond circularly polarized laser pulse (CPLP) in the presence of an orthogonal static electric field. This results in a chiral wavepacket that changes its chirality with the OOP frequency. We can probe this ultrafast oscillation using photoelectron circular dichroism with a second femtosecond CPLP. We numerically demonstrate this scheme’s applicability using a COFCl molecule as an example [2].

References

[1] Sun, W., Tikhonov, D.S., Singh, H. et al. // Nat Commun 14, 934 (2023).

[2] Denis S. Tikhonov et al. // Sci. Adv. 8, eade0311 (2022).

Dr. Denis Tikhonov graduated from Lomonosov Moscow State University (LMSU) in 2014 (Specialist degree), Faculty of Chemistry, and later, in 2017, got his Ph.D. (candidate of chemical sciences degree) in Physical Chemistry from the same institution. For two years during his Ph.D., he worked at the University of Bielefeld (Germany), doing research in the fields of gas electron diffraction and molecular dynamics. After Ph.D. Denis worked in an R&D lab at Geosplit LCC (Moscow, Skolkovo resident company) and also at the LMSU. In 2018, he went for a postdoc at DESY (Hamburg, Germany) to the group of Prof. Melanie Schnell, where he still resides. Denis’s current scientific interests are femtochemistry, theoretical spectroscopy, quantum control of chirality, molecular dynamics, and experimental data analysis.