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Direct observation of the collapse of the delocalized excess electron in water

Abstract

It is generally assumed that the hydrated electron occupies a quasi-spherical cavity surrounded by only a few water molecules in its equilibrated state. However, in the very moment of its generation, before water has had time to respond to the extra charge, it is expected to be significantly larger in size. According to a particle-in-a-box picture, the frequency of its absorption spectrum is a sensitive measure of the initial size of the electronic wavefunction. Here, using transient terahertz spectroscopy, we show that the excess electron initially absorbs in the far-infrared at a frequency for which accompanying ab initio molecular dynamics simulations estimate an initial delocalization length of ≈40 Å. The electron subsequently shrinks due to solvation and thereby leaves the terahertz observation window very quickly, within ≈200 fs.

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Figure 1: Terahertz response to photoionization of neat water.
Figure 2: Averaged radius of gyration rg (blue) and lowest excitation energy (green) of an excess electron attached to neat water system as a function of time.
Figure 3: Correlation between radius of gyration rg of the spin density and first excitation energy (blue dots).
Figure 4: Schematic depiction of excess electron formation and localization process in water.

References

  1. Garrett, B. C. et al. Role of water in electron-initiated processes and radical chemistry: issues and scientific advances. Chem. Rev. 105, 355–389 (2005).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  3. 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).

    Article  CAS  Google Scholar 

  4. Boag, J. W. & Hart, E. J. Absorption spectra in irradiated water and some solutions—absorption spectra of hydrated electron. Nature 197, 45–47 (1963).

    Article  CAS  Google Scholar 

  5. Chase, W. J. & Hunt, J. W. Solvation time of electron in polar liquids—water and alcohols. J. Phys. Chem. 79, 2835–2845 (1975).

    Article  CAS  Google Scholar 

  6. Wiesenfeld, J. M. & Ippen, E. P. Dynamics of electron solvation in liquid water. Chem. Phys. Lett. 73, 47–50 (1980).

    Article  CAS  Google Scholar 

  7. Migus, A., Gauduel, Y., Martin, J. L. & Antonetti, A. Excess electrons in liquid water—first evidence of a prehydrated state with femtosecond lifetime. Phys. Rev. Lett. 58, 1559–1562 (1987).

    Article  CAS  Google Scholar 

  8. McGowen, J. L., Ajo, H. M., Zhang, J. Z. & Schwartz, B. J. Femtosecond studies of hydrated electron recombination following multiphoton ionization at 390-nm. Chem. Phys. Lett. 231, 504–510 (1994).

    Article  CAS  Google Scholar 

  9. Pepin, C., Goulet, T., Houde, D. & Jay-Gerin, J. P. Observation of a continuous spectral shift in the solvation kinetics of electrons in neat liquid deuterated water. J. Phys. Chem. A 101, 4351–4360 (1997).

    Article  CAS  Google Scholar 

  10. Laenen, R., Roth, T. & Laubereau, A. Novel precursors of solvated electrons in water: evidence for a charge transfer process. Phys. Rev. Lett. 85, 50–53 (2000).

    Article  CAS  Google Scholar 

  11. Vilchiz, V. H., Kloepfer, J. A., Germaine, A. C., Lenchenkov, V. A. & Bradforth, S. E. Map for the relaxation dynamics of hot photoelectrons injected into liquid water via anion threshold photodetachment and above threshold solvent ionization. J. Phys. Chem. A 105, 1711–1723 (2001).

    Article  CAS  Google Scholar 

  12. Laenen, R. & Roth, T. Generation of solvated electrons in neat water: new results from femtosecond spectroscopy. J. Mol. Struct. 598, 37–43 (2001).

    Article  CAS  Google Scholar 

  13. Crowell, R. A. & Bartels, D. M. Multiphoton ionization of liquid water with 3.0–5.0 eV photons. J. Phys. Chem. 100, 17940–17949 (1996).

    Article  CAS  Google Scholar 

  14. Thomsen, C. L., Madsen, D., Keiding, S. R., Thogersen, J. & Christiansen, O. Two-photon dissociation and ionization of liquid water studied by femtosecond transient absorption spectroscopy. J. Chem. Phys. 110, 3453–3462 (1999).

    Article  Google Scholar 

  15. Bartels, D. M. & Crowell, R. A. Photoionization yield vs energy in H2O and D2O. J. Phys. Chem. A 104, 3349–3355 (2000).

    Article  CAS  Google Scholar 

  16. Sander, M. U., Gudiksen, M. S., Luther, K. & Troe, J. Liquid water ionization: mechanistic implications of the H/D isotope effect in the geminate recombination of hydrated electrons. Chem. Phys. 258, 257–265 (2000).

    Article  CAS  Google Scholar 

  17. Son, D. H., Kambhampati, P., Kee, T. W. & Barbara, P. F. Delocalizing electrons in water with light. J. Phys. Chem. A 105, 8269–8272 (2001).

    Article  CAS  Google Scholar 

  18. Kee, T. W., Son, D. H., Kambhampati, P. & Barbara, P. F. A unified electron transfer model for the different precursors and excited states of the hydrated electron. J. Phys. Chem. A 105, 8434–8439 (2001).

    Article  CAS  Google Scholar 

  19. Kambhampati, P., Son, D. H., Kee, T. W. & Barbara, P. F. Solvation dynamics of the hydrated electron depends on its initial degree of electron delocalization. J. Phys. Chem. A 106, 2374–2378 (2002).

    Article  CAS  Google Scholar 

  20. Lian, R., Oulianov, D. A., Shkrob, I. A. & Crowell, R. A. Geminate recombination of electrons generated by above-the-gap (12.4 eV) photoionization of liquid water. Chem. Phys. Lett. 398, 102–106 (2004).

    Article  CAS  Google Scholar 

  21. Elles, C. G., Jailaubekov, A. E., Crowell, R. A. & Bradforth, S. E. Excitation-energy dependence of the mechanism for two-photon ionization of liquid H2O and D2O from 8.3 to 12.4 eV. J. Chem. Phys. 125, 044515 (2006).

    Article  Google Scholar 

  22. Kratz, S., Torres-Alacan, J., Urbanek, J., Lindner, J. & Vöhringer, P. Geminate recombination of hydrated electrons in liquid-to-supercritical water studied by ultrafast time-resolved spectroscopy. Phys. Chem. Chem. Phys. 12, 12169–12176 (2010).

    Article  CAS  Google Scholar 

  23. Hertwig, A., Hippler, H. & Unterreiner, A. N. Transient spectra, formation, and geminate recombination of solvated electrons in pure water UV-photolysis: an alternative view. Phys. Chem. Chem. Phys. 1, 5633–5642 (1999).

    Article  CAS  Google Scholar 

  24. Birkedal, V. et al. Observation of a persistent infrared absorption following two photon ionization of liquid water. Chem. Phys. 328, 119–124 (2006).

    Article  CAS  Google Scholar 

  25. Coe, J. V. et al. Using cluster studies to approach the electronic structure of bulk water: reassessing the vacuum level, conduction band edge, and band gap of water. J. Chem. Phys. 107, 6023–6031 (1997).

    Article  CAS  Google Scholar 

  26. Turi, L. & Rossky, P. J. Theoretical studies of spectroscopy and dynamics of hydrated electrons. Chem. Rev. 112, 5641–5674 (2012).

    Article  CAS  Google Scholar 

  27. Uhlig, F., Marsalek, O. & Jungwirth, P. Unraveling the complex nature of the hydrated electron. J. Phys. Chem. Lett. 3, 3071–3075 (2012).

    Article  CAS  Google Scholar 

  28. Jacobson, L. D. & Herbert, J. M. Theoretical characterization of four distinct isomer types in hydrated-electron clusters, and proposed assignments for photoelectron spectra of water cluster anions. J. Am. Chem. Soc. 133, 19889–19899 (2011).

    Article  CAS  Google Scholar 

  29. Larsen, R. E., Glover, W. J. & Schwartz, B. J. Does the hydrated electron occupy a cavity? Science 329, 65–69 (2010).

    Article  CAS  Google Scholar 

  30. Casey, J. R., Kahros, A. & Schwartz, B. J. To be or not to be in a cavity: the hydrated electron dilemma. J. Phys. Chem. B 117, 14173–14182 (2013).

    Article  CAS  Google Scholar 

  31. Knoesel, E., Bonn, M., Shan, J. & Heinz, T. F. Charge transport and carrier dynamics in liquids probed by THz time-domain spectroscopy. Phys. Rev. Lett. 86, 340–343 (2001).

    Article  CAS  Google Scholar 

  32. Hare, P. M., Price, E. A. & Bartels, D. M. Hydrated electron extinction coefficient revisited. J. Phys. Chem. A 112, 6800–6802 (2008).

    Article  CAS  Google Scholar 

  33. Brown, M. S., Erickson, T., Frische, K. & Roquemore, W. M. Hot electron dominated rapid transverse ionization growth in liquid water. Opt. Express 19, 12241 (2011).

    Article  CAS  Google Scholar 

  34. Li, J., Nie, Z., Zheng, Y. Y., Dong, S. & Loh, Z-H. Elementary electron and ion dynamics in ionized liquid water. J. Phys. Chem. Lett. 4, 3698–3703 (2013).

    Article  CAS  Google Scholar 

  35. Crowell, R. A. et al. Light-induced temperature jump causes power-dependent ultrafast kinetics of electrons generated in multiphoton ionization of liquid water. J. Phys. Chem. A 108, 9105–9114 (2004).

    Article  CAS  Google Scholar 

  36. Mics, Z. et al. Nonresonant ionization of oxygen molecules by femtosecond pulses: plasma dynamics studied by time-resolved terahertz spectroscopy. J. Chem. Phys. 123, 104310 (2005).

    Article  Google Scholar 

  37. Pimblott, S. M. Independent pairs modeling of the kinetics following the photoionization of liquid water. J. Phys. Chem. 95, 6946–6951 (1991).

    Article  CAS  Google Scholar 

  38. Goulet, T. & Jay-Gerin, J. P. On the reactions of hydrated electrons with OH and H3O+—analysis of photoionization experiments. J. Chem. Phys. 96, 5076–5087 (1992).

    Article  CAS  Google Scholar 

  39. Němec, H., Kadlec, K. & Kužel, P. Methodology of an optical pump–terahertz probe experiment: an analytical frequency domain approach. J. Chem. Phys. 117, 8454 (2002).

    Article  Google Scholar 

  40. Kužel, P., Němec, H. & Kadlec, K. Propagation of THz pulses in photoexcited media: analytical theory for layered systems. J. Chem. Phys. 127, 024506 (2007).

    Article  Google Scholar 

  41. Xu, J., Plaxco, K. W., Allen, S. J., Bjarnason, J. E. & Brown, E. R. 0.15–3.72 THz absorption of aqueous salts and saline solutions. Appl. Phys. Lett. 90, 031908 (2007).

    Article  Google Scholar 

  42. Zelsmann, H. R. Temperature-dependence of the optical-constants for liquid H2O and D2O in the far IR region. J. Mol. Struct. 350, 95–114 (1995).

    Article  CAS  Google Scholar 

  43. Savolainen, J., Ahmed, S. & Hamm, P. Two-dimensional Raman-terahertz spectroscopy of water. Proc. Natl Acad. Sci. USA 110, 20402–20407 (2013).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

The authors thank S. Bradforth and P. Kužel for discussions. The work was supported in part by the Swiss National Science Foundation (SNF) through the NCCR MUST. P.J. acknowledges the Czech Science Foundation (grant P208/12/G016) for support and thanks the Academy of Sciences for the Praemium Academie award. F.U. and P.J. also acknowledge the computing time granted by the John von Neumann Institute for Computing (NIC) and provided on the supercomputer JUROPA at Jülich Supercomputing Centre (JSC).

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Contributions

J.S. and P.H. designed the experiments and analysed the data. J.S. and S.A. performed the experiments. P.J. and F.U. designed and analysed the computational part of the study and FU performed the calculations. P.H., P.J. and J.S. co-wrote the paper. J.S. and F.U. contributed equally to this work.

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Correspondence to Peter Hamm or Pavel Jungwirth.

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Savolainen, J., Uhlig, F., Ahmed, S. et al. Direct observation of the collapse of the delocalized excess electron in water. Nature Chem 6, 697–701 (2014). https://doi.org/10.1038/nchem.1995

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