Year: 2026
Type: preprint
Abstract: Nuclear quantum effects are essential for an accurate description of the hydrogen-bonded structure of liquid water, yet their spectroscopic signatures can be subtle and difficult to measure. Moreover, probing these effects in solution on femtosecond timescales (or below) is an open challenge that is pivotal for optical control of hydrogen bonds and ultrafast spectroscopy of proton transfer. Here, we combine path-integral molecular dynamics with real-time time-dependent density-functional theory to explore high-harmonic generation (HHG) in liquid water from first principles, rigorously accounting for quantum nuclear delocalisation. Relative to classical-nuclei simulations, quantum sampling suppresses the harmonic yield around certain harmonics by up to an order of magnitude, inducing local structural minima. By analysing the ab initio simulations and reproducing the key effects with a simplified model Hamiltonian, we trace the physical origins of the interference minima to the broadening of valence-band states induced by hydrogen-bond fluctuations, a mechanism expected to generalise to other hydrogen-bonded structures. Our work shows that nuclear quantum effects are indispensable for capturing ultrafast electronic dynamics in liquids, and demonstrates the power of liquid HHG spectroscopy for attosecond probing of nuclear fluctuations.
Source: arXiv (Cornell University)
Institutions: Center for Free-Electron Laser Science, Max Planck Institute for the Structure and Dynamics of Matter, Research Center Future Energy Materials and Systems, ETH Zurich, Laboratory of Physical Chemistry, Technion – Israel Institute of Technology, Ruhr University Bochum, University of Cambridge
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221924896