Chirality detection of gas-phase molecules at low concentrations is challenging as the molecular number density is usually too low to perform conventional circular dichroism absorption experiments. In recent years, new spectroscopic methods have been developed to detect chirality in the gas phase. In particular, the angular distribution of photoelectrons after multiphoton laser ionization of chiral molecules using circularly polarized light is highly sensitive to the enantiomeric form of the ionized molecule (multiphoton photoelectron circular dichro-ism (MP-PECD)). In the talk, I will present the MP-PECD as an analytic tool for chirality detection in heterogeneously catalyzed reactions. We recorded velocity resolved kinetics of styrene oxide desorption on Ag(111) using pulsed molecular beams with ion imaging techniques. In addition, we measured temperature-programmed desorption spectra of the same system. We combined both experimental techniques with enantiomer-specific detection by recording MP-PECD of desorbing reaction products using photoelectron imaging spectroscopy. We can clearly assign the enantiomeric form of the desorption product in sub-monolayer concentration. The results indicate no change in the chirality after ring opening on on Ag(111). The experiment demonstrates the combination of MP-PECD with surface science experiments, paving the way for enantiomer-specific detection of surface reaction products on heterogeneous catalysts for asymmetric synthesis.

Chirality detection in surface reactions using photoelectron circular dichroism

ACS Spring 2022

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