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Chiral molecules that are non-superimposable mirror images of each other, known as enantiomers, have identical chemical and physical properties unless they interact with another chiral entity, such as chiral light. Chiroptical effects arising from such interactions are used to detect enantiomers in mixtures and to induce enantioselective synthesis and catalysis. Chiroptical effects often arise from the interplay between light-induced electric- and magnetic-dipole transitions in a molecule and evolve on ultrafast electronic timescales. Here we use high-harmonic generation from a randomly oriented gas of molecules subjected to an intense laser field, to probe chiral interactions on these sub-femtosecond timescales. We show that a slight disparity in the laser-driven electron dynamics in the two enantiomers is recorded and amplified by several orders of magnitude in the harmonic spectra. Our work shows that chiroptical detection can go beyond detecting chiral structure to resolving and controlling chiral dynamics on electronic timescales. [ABSTRACT FROM AUTHOR]

Recollision processes provide direct insight into the structure and dynamics of electronic wave functions. However, the strength of the process sets its basic limitations--the interaction couples numerous degrees of freedom. In this Letter we decouple the basic steps of the process and resolve the role of the ionic potential which is at the heart of a broad range of strong field phenomena. Specifically, we measure high harmonic generation from argon atoms. By manipulating the polarization of the laser field we resolve the vectorial properties of the interaction. Our study shows that the ionic core plays a significant role in all steps of the interaction. In particular, Coulomb focusing induces an angular deflection of the electrons before recombination. A complete spatiospectral analysis reveals the influence of the potential on the spatiotemporal properties of the emitted light. [ABSTRACT FROM AUTHOR]

Conical intersections play a crucial role in the chemistry of most polyatomic molecules, ranging from the simplest bimolecular reactions to the photostability of DNA. The real-time study of the associated electronic dynamics poses a major challenge to the latest techniques of ultrafast measurement. We show that high-harmonic spectroscopy reveals oscillations in the electronic character that occur in nitrogen dioxide when a photoexcited wave packet crosses a conical intersection. At longer delays, we observe the onset of statistical dissociation dynamics. The present results demonstrate that high-harmonic spectroscopy could become a powerfu!, too[ to highlight electronic dynamics occurring along nonadiabatic chemical reaction pathways. [ABSTRACT FROM AUTHOR]