Core-Ionization Spectrum of Liquid Water

We present state-of-the-art calculations of the core-ionization spectrum of water. The values of experimentally derived solvation shifts in the core 1sO ionization energy of water vary from -1.3 to -2.8 eV due to difficulties in assessing the effect of the surface potential. This provides a motivation to obtain a robust theoretical value of the shift. Here we develop theoretical protocols based on coupled-cluster theory and electrostatic embedding. Our value of the solvent-induced shift of the core 1sO ionization energy of water is -1.51 eV. The computed absolute position and the width of the 1sO in photoelectron spectrum of water are 538.75 eV and 1.44 eV, respectively, agree well with the best experimental values.