In the fascinating realm of molecular science, chirality—or “handedness”—has long intrigued chemists and biologists alike. Just as our left and right hands are mirror images yet fundamentally different, many molecules exist in two mirror-image forms that are structurally identical but cannot be superimposed onto one another. This subtle difference has profound implications across biological systems, pharmaceuticals, and materials science. Now, a groundbreaking study from ETH Zurich, published in Nature, reveals a dynamic dimension to chirality that transcends static molecular structure, opening unprecedented avenues to observe and control electron behavior on attosecond time scales.
Chirality has traditionally been considered a geometric or structural property of molecules. The distinct left- or right-handed configurations of molecules such as amino acids and sugars dictate their biological functions and interactions. For instance, the chirality of a drug molecule determines whether it will be beneficial, inert, or even toxic within the human body. Despite this well-established paradigm, the static view of chirality neglects the ultrafast dynamics of the electron cloud that envelops these molecules, which can also exhibit handedness in their motion and interactions.
Addressing this limitation, Professor Hans Jakob Wörner and his research team have taken chirality research into entirely new territory by examining how electrons themselves behave differently when ejected from chiral molecules. Their approach harnesses an advanced technique that uses ultra-short bursts of circularly polarized light—attosecond pulses that last only a billionth of a billionth of a second—to probe electron ejection dynamics with extraordinary temporal precision. This innovation reveals for the first time that the electrons stripped from chiral molecules do not just reflect the structural handedness but possess their own directional handedness tied intimately to the chirality of the molecule and the light’s rotation.
The central phenomenon explored in the study is photoelectron circular dichroism (PECD), a quantum effect where an electron’s emission direction depends on the interplay between the molecule’s chirality and the helicity of the circularly polarized light used to excite it. Remarkably, the electrons do not eject symmetrically but preferentially along or opposite to the propagation direction of the light beam, depending on their mirror-image configurations. Observing PECD has so far been limited by technological constraints, but the newly developed attosecond pulse setup surmounts these barriers, allowing not only detection but also temporal manipulation of this effect.
Wörner’s team employed a sophisticated experimental arrangement combining circularly polarized attosecond pulses in the extreme ultraviolet (XUV) spectral range with a synchronized circularly polarized infrared pulse. This dual-pulse approach confers remarkable control: by adjusting the relative phase between the two pulses, the researchers can modulate the timing and direction of electron emission from chiral molecules. This technique unveils the ultrafast electron dynamics underlying PECD at their natural attosecond timescale and demonstrates that chirality manifests not just in static spatial arrangements but also in fleeting electron motions.
The experimental breakthrough is as much a technological feat as a conceptual advance. Generating circularly polarized attosecond pulses requires precision engineering of high-harmonic generation processes under carefully controlled conditions. By producing these tailored light flashes and synchronously overlaying them with infrared pulses, the team could visualize and actively steer chiral electron emissions in real time. This attosecond precision pushes the boundaries of chiral spectroscopy and electron dynamics, marking a new era where electron flow itself is explored as an intrinsic chiral property.
From a fundamental science perspective, the implications of this work extend far beyond the immediate ability to measure PECD. It challenges the long-held notion that chirality is exclusively a spatial qualifier by establishing chirality as a fundamentally dynamic electronic property. According to Meng Han, the study’s first author, the discovery that electron behavior in chiral molecules can be directly controlled on attosecond time scales invites rethinking of chiral phenomena, laying a foundation for manipulating molecular processes with unparalleled finesse.
The potential practical applications of these insights are equally profound. Chirality plays a defining role in the pharmaceutical industry, where the wrong enantiomer of a drug can cause adverse effects. Enhancing the sensitivity and specificity of chiral analysis through attosecond techniques could revolutionize drug design and safety testing. The attosecond flash spectroscopy and coherent control of electron emission dynamics might also facilitate novel synthetic pathways, enabling selective manipulation of chemical reactions based on molecular handedness.
Moreover, the new approach promises to provide answers to long-standing questions about the origins of molecular chirality in biological systems—a puzzle that touches on the fundamental nature of life itself. By observing how electronic motion evolves and is controlled in chiral molecules, scientists could gain fresh perspectives on the emergence and evolution of homochirality, a key feature of biochemical systems where only one handedness predominates.
Beyond chemistry and biology, the ability to control chirality at the electronic level heralds innovative possibilities in emerging fields such as spintronics, where electron spin and its manipulation underpin next-generation information processing technologies. The precise control over electron emission directionality might be harnessed to develop molecular-scale electronic devices and sensors that exploit chiral-induced spin selectivity for enhanced performance.
This breakthrough further aligns with the development of molecular machines and biosensors, as controlling electron dynamics with attosecond resolution and chiral specificity could enable intricate mechanical and sensing functions at the nanoscale. The fusion of attosecond physics with molecular chirality thus offers a powerful toolkit for advancing nanotechnology platforms that rely on dynamic electronic interactions.
In essence, this pioneering research by Wörner and his collaborators transcends the classical boundaries of chirality science. By illustrating that chirality is as much about the ultrafast behavior of electrons as it is about the arrangement of atoms, they have opened the door to a new understanding of how molecular asymmetry shapes the quantum world. This could transform theoretical and applied sciences, providing researchers with unprecedented control over the fundamental processes that govern molecular functionality.
The study epitomizes the convergence of quantum physics, chemistry, and ultrafast laser technology, demonstrating how cutting-edge experimental techniques can unravel phenomena previously hidden due to temporal or spatial constraints. As attosecond methodologies continue to mature, their integration into the study of chirality promises a rich harvest of insights, from elucidating complex biomolecular mechanisms to enabling novel technological applications rooted in the quantum characteristics of matter.
This research not only enriches our comprehension of the intricate dance of electrons within chiral molecules but also sets a compelling example of how probing the fastest processes in nature can reveal entirely new scientific vistas. The dynamic nature of chirality, as revealed through attosecond control of photoelectron emissions, beckons researchers to rethink conventional concepts and explore the full potential of chiral electronic phenomena in diverse scientific and technological domains.
Subject of Research:
Attosecond-scale electron dynamics in chiral molecules and their control via circularly polarized light.
Article Title:
Attosecond control and measurement of chiral photoionization dynamics.
Web References:
http://dx.doi.org/10.1038/s41586-025-09455-4
References:
Published in Nature; authors include Hans Jakob Wörner and Meng Han et al.
Keywords
Chirality, Photoelectron Circular Dichroism, Attosecond Pulses, Circularly Polarized Light, Electron Dynamics, Quantum Control, Ultrafast Spectroscopy, Molecular Asymmetry, Spintronics, Molecular Machines, Biosensors, High-Harmonic Generation
