Breakdown of the molecular orbital picture for X-ray emission of water

By measuring X-ray emission of the water molecule in liquid phase we establish a first example of Kshell X-ray emission spectra with strong breakdown of the molecular orbital picture. A complete splitting of the 2a1 1 peak into satellites is observed. A theoretical model with electronic configurations generated by coupled excitations/de-excitations, so-called semi-internal configuration interaction, captures the experimentally recorded features well. Differences with respect to the corresponding breakdown effect in ultraviolet photoelectron spectrum are highlighted. Molecular dynamics calculations indicate that solvent broadening can only make up for a small fraction of the width of the recorded 2a1 1 derived band.