# Non-equilibrium state during proton-deuteron exchange at a liquid-liquid interface

Source: [Non-equilibrium state during proton-deuteron exchange at a liquid-liquid interface](<https://www.sota2.com/research/paper/68fa4be71e209131ce949205>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2026-07-14T05:00:01.588Z

Authors: Tillmann Buttersack, Niclas Sven Mueller, Giulia Carini, Henrik Haak, Hanna Bordyuh, Dipali Singh, Sandy Gewinner, Marco De Pas, Wieland Sch\\"ollkopf, Martin Wolf, Hendrik Bluhm, Nils Huse, Bernd Winter, Gerard Meijer, Alexander Paarmann

Published: 2025-09-22T12:56:39.000Z

## Abstract

Proton-deuteron exchange is a very fast process, even across macroscopic length scales. Here we directly and quantitatively measure the formation of HDO within the first 100 microseconds of the reaction at the liquid-liquid interface between D$\_2$O and H$\_2$O, using a fast-flowing liquid flat jet combined with infrared spectroscopic imaging. We demonstrate that, at early stages HDO formation is reaction-limited, set by the low concentration of the hydroxide and hydronium ions that mediate the exchange. As the ion concentration rises, the rate rapidly approaches the diffusion limit. The reaction rate constant we extract is consistent with the picosecond timescale of the elementary proton-deuteron exchange. Access to these microsecond kinetics reveals a non-equilibrium state in the early H$\_2$O/D$\_2$O interface: the two liquids are fully mixed by diffusion, yet the HDO concentration remains well below equilibrium. Quantitative imaging of reactant and product concentrations at well-defined liquid-liquid interfaces, as introduced here, will enable the study of fast kinetics across a wide range of chemical reactions.

## Recorded benchmark results

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2509.17724>)

[PDF](<https://arxiv.org/pdf/2509.17724.pdf>)