Comment on 'Isotope and Temperature Effects in Liquid Water Probed by X-Ray Absorption and Resonant X-Ray Emission Spectroscopy'

摘要

Fuchs et al. [1] interpret the split lone-pair orbital (1b_1) in high-resolution x-ray emission spectra (XES) of liquid water based on core-hole dynamics leaving either intact molecular water (d_1 peak) or causing dissociation to an OH radical (d_2 peak), which they furthermore assume can be represented by OH~- anion. We find this picture, postulating emission either around the initial or the final structure, but not along the path connecting them, unphysical and unsubstantiated [2]. Figure 1 shows simulated XES spectra at t = 0 and integrated along core-hole induced trajectories, 10 fs long, with forces from Density Functional Theory [3]; random directions were assigned to the maximum velocities in the O-H stretch zero-point vibration. The initial geometries sample a molecular dynamics simulation representing predominantly tetrahedral structures, which is not necessarily representative of the liquid [4].