Strong laser pulses enable probing molecules with their own electrons, in a scheme referred to as laser-induced electron diffraction [1]. The oscillating electric field tears electrons off a molecule by tunnel-ionization, accelerates them and drives them back towards their parent ion within a few femtoseconds. The electrons are then diffracted by the molecular potential, encoding its structure and dynamics with Angström and attosecond resolutions. Using elliptically polarized laser pulses, we show that laser-induced electron diffraction is sensitive to the chirality of the target [2]. The field selectively ionizes molecules of a given orientation and drives the electrons along different sets of trajectories, leading them to recollide from different directions. Depending on the handedness of the molecule, the electrons are preferentially diffracted forward or backward along the light propagation axis. This asymmetry, reaching several %, can be reversed for electrons recolliding from two ends of the molecule. This strong chiral sensitivity of electron-molecule collisions had been predicted two decades ago [3], but never demonstrated up to now because of difficulties in controlling the orientation of the chiral molecules with respect to the electron beam. Strong-field ionization thus offers an unexpected solution to this issue, and opens a new path to resolve ultrafast chiral dynamics.

[1] K. Amini and J. Biegert, Ultrafast electron diffraction imaging of gas-phase molecules. Adv. At. Mol. Opt. Phys. 69, 163 (2020).

[2] D. Rajak et al., Laser-induced Electron Diffraction in Chiral Molecules, Phys. Rev. X (in press).

[3] A. Busalla, K. Blum, and D. G. Thompson, Differential Cross Section for Collisions between Electrons and Oriented Chiral Molecules. Phys. Rev. Lett. 83, 1562 (1999).