The absolute configuration of individual small molecules in the gas phase can be determined directly by light-induced Coulomb explosion imaging (CEI). Herein, this approach is demonstrated for ionization with a single X-ray photon from a synchrotron light source, leading to enhanced efficiency and faster fragmentation as compared to previous experiments with a femtosecond laser. In addition, it is shown that even incomplete fragmentation pathways of individual molecules from a racemic CHBrClF sample can give access to the absolute configuration in CEI. This leads to a significant increase of the applicability of the method as compared to the previously reported complete break-up into atomic ions and can pave the way for routine stereochemical analysis of larger chiral molecules by light-induced CEI.

Understanding the chirality of molecular reaction pathways is essential for a broad range of fundamental and applied sciences. However, the current ability to probe chirality on the time scale of primary processes underlying chemical reactions remains very limited. Here, we demonstrate time-resolved photoelectron circular dichroism (TRPECD) with ultrashort circularly polarized vacuum-ultraviolet (VUV) pulses from a tabletop source. We demonstrate the capabilities of VUV-TRPECD by resolving the chirality changes in time during the photodissociation of atomic iodine from two chiral molecules. We identify several general key features of TRPECD, which include the ability to probe dynamical chirality along the complete photochemical reaction path, the sensitivity to the local chirality of the evolving scattering potential, and the influence of electron scattering off dissociating photofragments. Our results are interpreted by comparison with high-level ab-initio calculations of transient PECDs from molecular photoionization calculations. Our experimental and theoretical techniques define a general approach to femtochirality.

The front cover artwork is provided by the groups of Reinhard Dörner (University of Frankfurt), Robert Berger (University of Marburg) and Jürgen Stohner (Zurich University for Applied Sciences, Wädenswil). The image shows how a single X‐ray photon from a synchrotron source induces the Coulomb Explosion of a prototypical chiral molecule (CHBrClF), allowing to distinguish the enantiomers and determine the absolute configuration. Read the full text of the article at 10.1002/cphc.201501118.

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The enantiomers of bromofluoroiodomethane (CHBrFI) were separated on a preparative scale using gas chromatography (GC). The collected single enantiomers were analysed by vibrational circular dichroism spectroscopy and polarimetry in combination with ab initio calculations to determine the respective absolute configuration.