Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions.

Biomolecular radiation damage is largely mediated by radicals and low-energy electrons formed by water ionization rather than by direct ionization of biomolecules. It was speculated that such an extensive, localized water ionization can be caused by ultrafast processes following excitation by core-level ionization of hydrated metal ions. In this model, ions relax via a cascade of local Auger-Meitner and, importantly, non-local charge- and energy-transfer processes involving the water environment. Here, we experimentally and theoretically show that, for solvated paradigmatic intermediate-mass Al3+ ions, electronic relaxation involves two sequential solute-solvent electron transfer-mediated decay processes. The electron transfer-mediated decay steps correspond to sequential relaxation from Al5+ to Al3+ accompanied by formation of four ionized water molecules and two low-energy electrons. Such charge multiplication and the generated highly reactive species are expected to initiate cascades of radical reactions.

Synchrotron radiation study of chloromethane clusters: effects of polarizability and dipole moment on core level chemical shifts.

Free neutral chloromethane clusters have been produced by adiabatic expansion and investigated by means of photoelectron spectroscopy. By studying the differences between the cluster binding energy shifts at the Cl 2p and C 1s thresholds we have shown that antiparallel packing is the dominant local structure of the clusters. This geometry is induced by the polar character of the constituent molecules, and it accords with the structures of chloromethane solids and dimers. Furthermore, results obtained from the analysis of the outer valence levels of the clusters support the suggested local structure. The roles of the polarizability and of the dipole moment of the constituent molecules in the cluster binding energy shifts are discussed in comparison with a recent investigation of bromomethane clusters.

Postcollision interaction in noble gas clusters: observation of differences in surface and bulk line shapes.

The surface and bulk components of the x-ray photoelectron spectra of free noble gas clusters are shown to display differences in the influence of postcollision interaction between the photoelectron and the Auger electron on the spectral line shape; the bulk component is observed to be less affected than the surface and atomic parts of the spectra. A model for postcollision interaction in nonmetallic solids and clusters is also provided which takes the polarization screening into account. Core-level photoelectron spectra of Ar, Kr, and Xe have been recorded to verify the dependence of the postcollision interaction effect on the polarizability of the sample.