Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Spectroscopic evidence for a gold-coloured metallic water solution



Insulating materials can in principle be made metallic by applying pressure. In the case of pure water, this is estimated1 to require a pressure of 48 megabar, which is beyond current experimental capabilities and may only exist in the interior of large planets or stars2,3,4. Indeed, recent estimates and experiments indicate that water at pressures accessible in the laboratory will at best be superionic with high protonic conductivity5, but not metallic with conductive electrons1. Here we show that a metallic water solution can be prepared by massive doping with electrons upon reacting water with alkali metals. Although analogous metallic solutions of liquid ammonia with high concentrations of solvated electrons have long been known and characterized6,7,8,9, the explosive interaction between alkali metals and water10,11 has so far only permitted the preparation of aqueous solutions with low, submetallic electron concentrations12,13,14. We found that the explosive behaviour of the water–alkali metal reaction can be suppressed by adsorbing water vapour at a low pressure of about 10−4 millibar onto liquid sodium–potassium alloy drops ejected into a vacuum chamber. This set-up leads to the formation of a transient gold-coloured layer of a metallic water solution covering the metal alloy drops. The metallic character of this layer, doped with around 5 × 1021 electrons per cubic centimetre, is confirmed using optical reflection and synchrotron X-ray photoelectron spectroscopies.

Your institute does not have access to this article

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: A pure NaK drop in vacuum and the time evolution of a NaK drop exposed to water vapour.
Fig. 2: Schematic demonstrating the formation of a thin gold-coloured metallic water layer by water vapour adsorption on a NaK drop.
Fig. 3: Spectroscopic signatures of the metallic water solution from optical and X-ray photoelectron spectroscopy.
Fig. 4: Fits to the experimental data employing a free electron gas model.

Data availability

The datasets generated during the current study are available as Source Data or are available from the corresponding author upon reasonable request. Source data are provided with this paper.

Code availability

Data-processing and fitting results can be generated using numerical methods described in Methods and Supplementary Information and developed computer codes that are available from the corresponding author upon reasonable request.


  1. Hermann, A., Ashcroft, N. W. & Hoffmann, R. High pressure ices. Proc. Natl Acad. Sci. USA 109, 745–750 (2012).

    ADS  CAS  Article  Google Scholar 

  2. Dubrovinsky, L., Dubrovinskaia, N., Prakapenka, V. B. & Abakumov, A. M. Implementation of micro-ball nanodiamond anvils for high-pressure studies above 6 Mbar. Nat. Commun. 3, 1163 (2012).

    ADS  Article  Google Scholar 

  3. Cavazzoni, C. et al. Superionic and metallic states of water and ammonia at giant planet conditions. Science 283, 44–46 (1999).

    ADS  CAS  Article  Google Scholar 

  4. Mattsson, T. R. & Desjarlais, M. P. Phase diagram and electrical conductivity of high energy-density water from density functional theory. Phys. Rev. Lett. 97, 017801 (2006).

    ADS  Article  Google Scholar 

  5. Millot, M. et al. Nanosecond X-ray diffraction of shock-compressed superionic water ice. Nature 569, 251–255 (2019).

    ADS  CAS  Article  Google Scholar 

  6. Zurek, E., Edwards, P. P. & Hoffmann, R. A molecular perspective on lithium-ammonia solutions. Angew. Chem. Int. Ed. 48, 8198–8232 (2009).

    CAS  Article  Google Scholar 

  7. Thompson, J. C. Electrons in Liquid Ammonia (Clarendon Press, 1976).

  8. Lodge, M. et al. Multielement NMR studies of the liquid-liquid phase separation and the metal-to-nonmetal transition in fluid lithium- and sodium-ammonia solutions. J. Phys. Chem. B 117, 13322–13334 (2013).

    CAS  Article  Google Scholar 

  9. Buttersack, T. et al. Photoelectron spectra of alkali metal-ammonia microjets: from blue electrolyte to bronze metal. Science 368, 1086–1091 (2020).

    ADS  CAS  Article  Google Scholar 

  10. Hutton, A. T. Dramatic demonstration for a large audience: the formation of hydroxyl ions in the reaction of sodium with water. J. Chem. Educ. 58, 506 (1981).

    CAS  Article  Google Scholar 

  11. Mason, P. E. et al. Coulomb explosion during the early stages of the reaction of alkali metals with water. Nat. Chem. 7, 250–254 (2015).

    ADS  CAS  Article  Google Scholar 

  12. Young, R. M. & Neumark, D. M. Dynamics of solvated electrons in clusters. Chem. Rev. 112, 5553–5577 (2012).

    CAS  Article  Google Scholar 

  13. Mason, P. E., Buttersack, T., Bauerecker, S. & Jungwirth, P. A non-exploding alkali metal drop on water: from blue solvated electrons to bursting molten hydroxide. Angew. Chem. Int. Ed. 55, 13019–13022 (2016).

    CAS  Article  Google Scholar 

  14. Suzuki, T. Ultrafast photoelectron spectroscopy of aqueous solutions. J. Chem. Phys. 151, 090901 (2019).

    ADS  Article  Google Scholar 

  15. Alchagirov, B. B. et al. Surface tension and adsorption of components in the sodium–potassium alloy systems: effective liquid metal coolants promising in nuclear and space power engineering. Inorg. Mater. Appl. Res. 2, 461–467 (2011).

    Article  Google Scholar 

  16. Addison, C. C. The Chemistry of Liquid Alkali Metals (Wiley, 1984).

  17. Citrin, P. H. High-resolution X-ray photoemission from sodium metal and its hydroxide. Phys. Rev. B 8, 5545–5556 (1973).

    ADS  CAS  Article  Google Scholar 

  18. Lueth, H. Surfaces and Interfaces of Solid Materials (Springer, 1997).

  19. Kiskinova, M., Pirug, G. & Bonzel, H. P. Adsorption and decomposition of H2O on a K-covered Pt(111) surface. Surf. Sci. 150, 319–338 (1985).

    ADS  CAS  Article  Google Scholar 

  20. Blass, P. M., Zhou, X. L. & White, J. M. Coadsorption and reaction of water and potassium on Ag(111). J. Phys. Chem. 94, 3054–3062 (1990).

    CAS  Article  Google Scholar 

  21. Nachtrieb, N. H. Self-diffusion in liquid metals. Adv. Phys. 16, 309–323 (1967).

    ADS  CAS  Article  Google Scholar 

  22. Ketteler, G. et al. The nature of water nucleation sites on TiO2(110) surfaces revealed by ambient pressure X-ray photoelectron spectroscopy. J. Phys. Chem. C 111, 8278–8282 (2007).

    CAS  Article  Google Scholar 

  23. Kittel, C. Introduction to Solid State Physics (Wiley, 2005).

  24. Abelès, F., Borensztein, Y., Decrescenzi, M. & Lopezrios, T. Optical evidence for longitudinal-waves in very thin Ag layers. Surf. Sci. 101, 123–130 (1980).

    ADS  Article  Google Scholar 

  25. Winter, B., Faubel, M., Vacha, R. & Jungwirth, P. Behavior of hydroxide at the water/vapor interface. Chem. Phys. Lett. 474, 241–247 (2009).

    ADS  CAS  Article  Google Scholar 

  26. Bonzel, H. P., Pirug, G. & Winkler, A. Adsorption of H2O on potassium films. Surf. Sci. 175, 287–312 (1986).

    ADS  CAS  Article  Google Scholar 

  27. Hart, E. J. & Boag, J. W. Absorption spectrum of hydrated electron in water and in aqueous solutions. J. Am. Chem. Soc. 84, 4090–4095 (1962).

    CAS  Article  Google Scholar 

  28. Barzynski, H. & Schulte-Frohlinde, D. On the nature of the electron traps in alkaline ice. Z. Naturforsch. A 22, 2131–2132 (1967).

    ADS  CAS  Article  Google Scholar 

  29. Kevan, L. Slovated electron structure in glassy matrices. Acc. Chem. Res. 14, 138–145 (1981).

    CAS  Article  Google Scholar 

  30. Buttersack, T. et al. Deeply cooled and temperature controlled microjets: liquid ammonia solutions released into vacuum for analysis by photoelectron spectroscopy. Rev. Sci. Instrum. 91, 043101 (2020).

    ADS  CAS  Article  Google Scholar 

  31. Seidel, R., Pohl, M. N., Ali, H., Winter, B. & Aziz, E. F. Advances in liquid phase soft-X-ray photoemission spectroscopy: a new experimental setup at BESSY II. Rev. Sci. Instrum. 88, 073107 (2017).

  32. Sawhney, K. J. S., Senf, F. & Gudat, W. PGM beamline with constant energy resolution mode for U49-2 undulator at BESSY-II. Nucl. Instrum. Methods Phys. Res. Sect. A 467, 466–469 (2001).

Download references


P.J. acknowledges support from the European Regional Development Fund (project ChemBioDrug number CZ.02.1.01/0.0/0.0/16_019/0000729). D.M.N. and C.L. acknowledge support from the Director of the Office of Basic Energy Science, Chemical Sciences Division of the US Department of Energy under contract number DE-AC02-05CH11231. D.M.N., C.L. and P.J. thank the Alexander von Humboldt Foundation for support. S.E.B., T.B. and R.S.M. are supported by the US National Science Foundation (CHE-1665532). P.E.M. acknowledges support from the viewers of his YouTube popular science channel. M.V. acknowledges support from the Charles University in Prague and from the International Max Planck Research School in Dresden. S.T. acknowledges support from JSPS KAKENHI grant number JP18K14178. R.S. acknowledges the German Research Foundation (DFG) for an Emmy-Noether Young-Investigator stipend (DFG, project SE 2253/3-1). F.T. and B.W. acknowledge support from the MaxWater initiative of the Max-Planck-Gesellschaft. All authors thank the staff of the Helmholtz-Zentrum Berlin for their support during the beamtime at BESSY II.

Author information

Authors and Affiliations



P.E.M., H.C.S., T.B., B.W., S.E.B. and P.J. designed the experiments. P.E.M., H.C.S., T.B., B.W., H.A., V.K., M.V., F.T., C.L., D.M.N., R.S. and P.J. performed the experiments, and P.E.M., H.C.S., T.B., B.W., S.E.B., R.S.M., C.L., R.S., S.T. and P.J. analysed the obtained data. P.J. wrote the main paper, and H.C.S. and P.J. wrote the Supplementary Information, both with critical feedback from all co-authors. P.E.M. produced Supplementary Video 1.

Corresponding author

Correspondence to Pavel Jungwirth.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Christoph Salzmann and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

This Supplementary Information file contains the following sections: (1) Sample preparation and employment in the experimental setup; (2) Photoelectron spectroscopy measurements; (3) Photoelectron spectra of pure NaK jets versus drops; (4) Photoelectron spectra of water vapour adsorbing on the NaK drop surface; (5) Data-analysis of photoelectron spectra acquired in fixed-mode operation; (6) Data-fitting of photoelectron spectra; (7) Optical reflection spectroscopy; and (8) Supplementary References

Supplementary Video 1

A detailed description of the experimental setup and conduction of the experiments.

Peer Review File

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Mason, P.E., Schewe, H.C., Buttersack, T. et al. Spectroscopic evidence for a gold-coloured metallic water solution. Nature 595, 673–676 (2021).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing