VIE_vac,1b1(l) and VIE_vac,O1s(l) values of the liquid water valence 1b₁ band and O 1s core-level peaks, respectively. The values were extracted from the spectra measured at different photon energies using the absolute referencing analysis method, Method 2. These values represent the averages of all measurements performed at the respective photon energy. The values in bold font are deemed to be essentially free of electron scattering based distortions of the measured VIE_vac values, while still being minimally affected by spectral distortions associated with the applied bias. The VIE_vac values shown in bold font can alternatively be referenced to the Fermi level, VIE_EF. Such values can be ascertained by subtracting the work function of liquid water, eΦ_water, determined here from the VIE_vac values. See the main body of the text for further details.

Measured at	hν (eV)		VIEvac,1b1(l) (eV)		VIEvac,O1s(l) (eV)
DESIRS, SOLEIL	15.00	±0.03	11.82	±0.08
DESIRS, SOLEIL	19.99	±0.03	11.58	±0.07
Laboratory, FHI Berlin	21.218	±0.001	11.48	±0.05
DESIRS, SOLEIL	24.98	±0.03	11.38	±0.04
DESIRS, SOLEIL	29.97	±0.030	11.35	±0.04
Laboratory, FHI Berlin	40.814	±0.001	11.34	±0.03
Laboratory, FHI Berlin	48.372	±0.001	11.35	±0.03
U49-2_PGM-1, BESSY II	123.464	±0.004	11.33	±0.03
U49-2_PGM-1, BESSY II	246.927	±0.005	11.32	±0.04
P04, PETRA III	249.99	±0.02	11.28	±0.04
P04, PETRA III	400.01	±0.03	11.31	±0.04
U49-2_PGM-1, BESSY II	400.868	±0.004	11.27	±0.05
P04, PETRA III	650.03	±0.03	11.27	±0.05	538.08	±0.05
U49-2_PGM-1, BESSY II	649.67	±0.03	11.31	±0.06	538.13	±0.05
U49-2_PGM-1, BESSY II	867.29	±0.01	11.32	±0.09	538.07	±0.07
P04, PETRA III	950.06	±0.03	11.33	±0.09	538.04	±0.08