Auger Spectrum of a Water Molecule after Single and Double Core-Ionization by Intense X-Ray Radiation

Abstract

The high intensity of new x-ray sources such as Free Electron Lasers (FEL) offers the possibility to do single-shot molecule diffraction experiments. Even for small molecules, the dynamics induced by the radiation damage in such experiments are not yet fully understood. In particular, double core-ionized molecules are expected to be created in considerable quantity. We have therefore studied the electronic and nuclear dynamics of water molecules in single and double core ionized states by means of electronic transition rates and ab initio molecular dynamics (MD) simulations. From MD trajectories Auger transition rates were computed based on continuum electronic wavefunctions obtained by explicit integration of the coupled radial Schrödinger equations. The calculated spectra for different molecular geometries were accumulated to account for the effects of nuclear dynamics during the core-hole lifetime. In contrast to the single core ionized water molecule, we found that dissociation dynamics of double core-ionized water have strong effect on the resulting electron emission spectra. In addition, we found that the single core hole lifetime is slightly smaller than the value obtained in earlier theoretical works. Finally, we predict that the lifetime of double core ionized states is significantly lower than half of the lifetime of a single core hole.