The role of metal ions in X-ray induced photochemistry

TL;DR

This study investigates how X-ray absorption by metal ions causes ultrafast relaxation cascades, leading to environmental degradation and implications for radiation chemistry and biomolecular damage.

Contribution

The paper provides the first ab initio analysis of X-ray induced relaxation cascades in microsolvated metal ions, revealing detailed ultrafast processes and their biological relevance.

Findings

X-ray absorption causes rapid electronic cascades in Mg ions.

The metal ion reverts to its original charge state after the cascade.

Large concentrations of radicals and slow electrons form near the metal.

Abstract

Metal ions play numerous important roles in biological systems being central to the function of biomolecules. In this letter we show that the absorption of X-rays by these ions leads to a complicated chain of ultrafast relaxation steps resulting in the complete degradation of their nearest environment. We conducted high quality ab initio studies on microsolvated Mg clusters demonstrating that ionisation of an 1s-electron of Mg leads to a complicated electronic cascade comprising both intra- and intermolecular steps and lasting only a few hundreds femtoseconds. The metal cation reverts to its original charge state at the end of the cascade, while the nearest solvation shell becomes multiply ionised and large concentrations of radical and slow electron species build up in the metal vicinity. We conclude that such cascades involving metal ions are essential for understanding the radiation chemistry of solutions and radiation damage to metal containing biomolecules.