Single photon double ionization of the helium dimer

TL;DR

This study demonstrates that a single photon can ionize both helium atoms in a helium dimer at large distances, revealing details about the molecular wave function through Coulomb explosion imaging.

Contribution

It provides the first direct observation of photon-induced double ionization in a highly diffuse molecule, linking ionization dynamics with the molecular wave function.

Findings

Double ionization occurs at distances up to 10 Å.

The process resembles a knock-off ionization mechanism.

Coulomb explosion imaging visualizes the nuclear wave function.

Abstract

We show that a single photon can ionize the two helium atoms of the helium dimer in a distance up to 10 {\deg}A. The energy sharing among the electrons, the angular distributions of the ions and electrons as well as comparison with electron impact data for helium atoms suggest a knock-off type double ionization process. The Coulomb explosion imaging of He_2 provides a direct view of the nuclear wave function of this by far most extended and most diffuse of all naturally existing molecules.