Observation of core-hole double excitations in water using fluorescence spectroscopy

Abstract

The hydrogen Lyman-$\ensuremath{\alpha}$, Balmer-$\ensuremath{\alpha}$, and Balmer-$\ensuremath{\beta}$ emission has been measured from the ${\mathrm{H}}_{2}\mathrm{O}$ molecule at photon energies exceeding the $1s$ ionization threshold. Fluorescence emission is shown to be a sensitive probe to neutral core-hole doubly excited states and singly ionized $1s$ shake-up states that are embedded in the core ionization continuum. In addition, the photoabsorption spectrum of the water molecule in the energy range of the double excitations has been measured with better statistics than previously.