Research ArticleChemistry

Genuine binding energy of the hydrated electron

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Science Advances  28 Apr 2017:
Vol. 3, no. 4, e1603224
DOI: 10.1126/sciadv.1603224
  • Fig. 1 Energy diagram of photoionization.

    The ground-state hydrated electron eaq is ionized by the ionization laser hν. Esca is the energy loss due to scattering, eKE is the recorded electron kinetic energy, and eBE(g) is the genuine electron binding energy (Eq. 2). V0 is the location of the conduction band edge of water relative to the vacuum level (“escape barrier”).

  • Fig. 2 Experimental and simulated photoelectron spectra of eaq.

    Photoelectron kinetic energy distributions for 12 different ionization laser energies 3.6 eV ≤ hν ≤ 13.6 eV. All spectra are normalized to the same maximum intensity. (A) Experimental spectra. (B) Scattering simulations (section S2 and fig. S5).

  • Fig. 3 eBE spectra of eaq.

    eBE spectra for 12 different ionization laser energies 3.6 eV ≤ hν ≤ 13.6 eV (lines). The stars represent the genuine eBE(g) spectrum; that is, the spectrum devoid of scattering contributions. The genuine VBE(g) is 3.7 ± 0.1 eV. For clarity, only the calculated data from Fig. 2 are shown here. See fig. S9 for a comparison with the experiment.

  • Fig. 4 Energy-dependent probing depth of eaq.

    Probing depths as a function of the ionization laser energy hν. Black circles, probing depth corresponding to 63% of the total electron signal; blue crosses, probing depth corresponding to 80% of the total electron signal.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/4/e1603224/DC1

    Supplementary Text

    Supplementary Materials and Methods

    section S1. Experimental values for the VBE of the bulk hydrated electron

    section S2. Description of scattering calculations

    section S3. Description of experimental setup

    section S4. Additional eKE distributions

    section S5. Sensitivity of eKE distributions to scattering parameters

    section S6. Additional electron binding energy spectra

    section S7. Probing depth and surface sensitivity

    section S8. Photoelectron angular distribution

    table S1. Previously reported values of the VBEs for the bulk hydrated electron.

    fig. S1. Experimental VBEs by Yamamoto et al. (8).

    fig. S2. Light intensity distribution in the liquid microjet.

    fig. S3. Integral scattering cross sections for electrons in water as a function of the eKE as derived by Signorell et al. and Michaud et al. (35, 39).

    fig. S4. Scheme of the experimental setup.

    fig. S5. Direct comparison of the experimental and calculated photoelectron kinetic energy distributions from Fig. 2 for all probe energies hν.

    fig. S6. The influence of scattering on the eKE distributions.

    fig. S7. Sensitivity of eKE distributions to an increase in the inelastic mean free path (IMFP) of +40%, which corresponds to the upper uncertainty limit of the IMFP (35).

    fig S8. Sensitivity of eKE distributions to a change in the angular distribution of the inelastic scattering events (section S2).

    fig. S9. Experimental eBE spectra for the different photon energies between 3.6 eV ≤ hν ≤ 13.6 eV.

    fig. S10. Uncertainty of the eBE(g) spectrum.

    fig. S11. Fraction of the total electron intensity that originates from cylindrical shells of various thickness for photon energies 3.6 eV ≤ hν ≤ 13.6 eV and for a photon energy hν = 38.7 eV (red, dashed line) (6).

    fig. S12. Surface contribution to the eBE spectra for (A) hν = 3.6 eV and (B) hν = 5.8 eV.

    fig. S13. Calculated angle-dependent liquid jet photoelectron spectra for different ionization laser polarization directions 0° ≤ θ ≤ 90° (section S2 and fig. S4) and a photon energy of hν = 4.8 eV (23).

    fig. S14. Calculated velocity map photoelectron image for hydrated electrons in an anion cluster with ~50 H2O molecules for a genuine anisotropy parameter β(g) = 0.6 and a photon energy of hν = 3.1 eV (45).

    References (4757)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Supplementary Materials and Methods
    • section S1. Experimental values for the VBE of the bulk hydrated electron
    • section S2. Description of scattering calculations
    • section S3. Description of experimental setup
    • section S4. Additional eKE distributions
    • section S5. Sensitivity of eKE distributions to scattering parameters
    • section S6. Additional electron binding energy spectra
    • section S7. Probing depth and surface sensitivity
    • section S8. Photoelectron angular distribution
    • table S1. Previously reported values of the VBEs for the bulk hydrated electron.
    • fig. S1. Experimental VBEs by Yamamoto et al. (8).
    • fig. S2. Light intensity distribution in the liquid microjet.
    • fig. S3. Integral scattering cross sections for electrons in water as a function of the eKE as derived by Signorell et al. and Michaud et al. (35, 39).
    • fig. S4. Scheme of the experimental setup.
    • fig. S5. Direct comparison of the experimental and calculated photoelectron kinetic energy distributions from Fig. 2 for all probe energies hν.
    • fig. S6. The influence of scattering on the eKE distributions.
    • fig. S7. Sensitivity of eKE distributions to an increase in the inelastic mean free path of +40%, which corresponds to the upper uncertainty limit of the IMFP (35).
    • fig S8. Sensitivity of eKE distributions to a change in the angular distribution of the inelastic scattering events (section S2).
    • fig. S9. Experimental eBE spectra for the different photon energies between 3.6 eV ≤ hν ≤ 13.6 eV.
    • fig. S10. Uncertainty of the eBE(g) spectrum.
    • fig. S11. Fraction of the total electron intensity that originates from cylindrical shells of various thickness for photon energies 3.6 eV ≤ hν ≤ 13.6 eV and for a photon energy hν = 38.7 eV (red, dashed line) (6).
    • fig. S12. Surface contribution to the eBE spectra for (A) hν = 3.6 eV and (B) hν = 5.8 eV.
    • fig. S13. Calculated angle-dependent liquid jet photoelectron spectra for different ionization laser polarization directions 0° ≤ θ ≤ 90° (section S2 and fig. S4) and a photon energy of hν = 4.8 eV (23).
    • fig. S14. Calculated velocity map photoelectron image for hydrated electrons in an anion cluster with ~50 H2O molecules for a genuine anisotropy parameter
      β(g) = 0.6 and a photon energy of hν = 3.1 eV (45).
    • References (47–57)

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