Attosecond spectroscopy: observing electron dynamics in molecules, clusters and liquids

Attosecond spectroscopy enables the direct observation of electron dynamics on their natural timescale. Its ability to freeze nuclear motion on the shortest time scales constitutes a powerful approach to understanding the complex interplay of electronic and nuclear dynamics that underlies chemistry.
In molecules, attosecond transient-absorption spectroscopy reveals purely electronic charge migration, including its decoherence and revival driven by nuclear motion and the transfer of electronic coherence through conical intersections [1]. It resolves charge-transfer dynamics at conical intersections, including a measurable ~1.5-fs delay in population transfer that reflects a non-instantaneous multi-electron rearrangement [2]. Extending to more complex systems, attosecond spectroscopy of water clusters uncovers how the spatial extension of electronic wavefunctions evolves with system size [3], while studies in liquids identify the roles of solvation and electron transport in photoionization dynamics [4] and disentangle electronic from structural dynamics during proton transfer in aqueous solution [5]. A recent breakthrough is the ability of generating and fully characterizing circularly polarized attosecond pulses, which enable the measurement and control of electron dynamics and photoionization delays of chiral molecules, opening new perspectives for controlling chiral dynamics on electronic time scales [6].

[1] D. Matselyukh, et al. Nat. Phys. 18, 1206 (2022)
[2] D. Matselyukh et al., Nat. Comm. 16, 7211 (2025)
[3] X. Gong et al., Nature 609, 507 (2022)
[4] I. Jordan et al., Science 369, 974 (2020)
[5] Z. Yin et al., Nature 619, 749 (2023)
[6] M. Han et al., Nature 645, 95 (2025)