# Highly efficient double ionization of mixed alkali dimers by intermolecular Coulombic decay

## TL;DR

This paper uncovers a highly efficient intermolecular Coulombic decay mechanism causing double ionization in alkali dimers on helium droplets, with implications for understanding radiation damage in biological systems.

## Contribution

It introduces a new intermolecular decay process leading to double ionization, surpassing single ionization efficiency, in weakly bound complexes like alkali dimers on helium droplets.

## Key findings

- Double ionization efficiency exceeds single ionization.
- Decay mechanism similar to shake-off in Auger processes.
- Relevance extends to biological radiation damage mechanisms.

## Abstract

As opposed to purely molecular systems where electron dynamics proceed only through intramolecular processes, weakly bound complexes such as He droplets offer an environment where local excitations can interact with neighbouring embedded molecules leading to new intermolecular relaxation mechanisms. Here, we report on a new decay mechanism leading to the double ionization of alkali dimers attached to He droplets by intermolecular energy transfer. From the electron spectra, the process is similar to the well-known shake-off mechanism observed in double Auger decay and single-photon double ionization, however, in this case, the process is dominant, occurring with efficiencies equal to, or greater than, single ionization by energy transfer. Although an alkali dimer attached to a He droplet is a model case, the decay mechanism is relevant for any system where the excitation energy of one constituent exceeds the double ionization potential of another neighbouring molecule. The process is, in particular, relevant for biological systems, where radicals and slow electrons are known to cause radiation damage