Austen in Amsterdam: Isotope effect in a liquid-liquid transition in supercooled aqueous solution

We investigate the H/D isotope effect in a liquid-liquid transition in crystallization-resistant supercooled aqueous solution. Using steady-state infrared spectroscopy and measuring thermal conductivities, we observe a ≈5 K shift in the onset temperature of the liquid-liquid transition, a value that is similar to the H/D isotope shifts of the HDA-LDA transition and of the Widom line of pure supercooled water [Kim et al., Science 358, 1589 (2017)], and that highlights the importance of isotope effects in water's supercooled regime. By employing multivariate data analysis we find isosbestic point related to the phase transformation in both isotopic systems, indicating phase coexistence during the transition. This article is dedicated to the memory of Austen Angell, and we begin with some personal memories of his two stays at the University of Amsterdam.