Low-Attosecond Resolution Electronic and Nuclear Dynamics: How Helical Electron Motion Drives Chiral Asymmetry

Controlling and observing electron motion in chiral molecules is a fundamental challenge spanning chemical synthesis, materials science, and spintronics. The electronic origin of chiral asymmetry is revealed by combining real-space analysis of the total electronic charge density with time-dependent density functional theory (DFT) electron-nuclear dynamics simulations. Using simulated ultrafast circularly polarized laser pulses, the correct enantiomeric assignment for (S)-1-chloro-1-fluoroethane is demonstrated. Modulating the carrier envelope phase (CEP) angle altered the so-called extrinsic electronic chirality in both chiral (S)-1-chloro-1-fluoroethane and achiral chloroethane. Helical bound electron motion, quantified as intrinsic electronic chirality, however, was uniquely observed in the structurally chiral molecule and tuned to induce a significant degree of electronic achiral character via CEP variation. Furthermore, eigenvector-space trajectories exhibited distinct 3-D and 1-D morphologies for chiral (S)-1-chloro-1-fluoroethane and achiral chloroethane, respectively. This framework provides the molecular-level design principles needed to transition from static structural descriptors to dynamic electronic properties that can directly impact future practical applications, particularly in asymmetric synthesis and the design of next-generation chiral materials, such as those that exploit the chirality-induced spin selectivity (CISS) effect.