Abstract
When an atom is electronically excited, it relaxes by emitting a photon or an electron. These carry essential information on the electronic structure of their emitter.
However, if an atom is embedded in a chemical environment, another ultrafast non-radiative decay process called interatomic Coulombic decay (ICD) can become operative. A key feature of ICD is that the excited atom can transfer its excess energy to its neighbours over large distances.
The giant extremely weakly bound helium dimer is a perfect candidate to investigate how far two atoms can exchange energy. We report here that the two helium atoms within the dimer can exchange energy by ICD over distances of more than 45 times their atomic radius.
Moreover, we demonstrate that ICD spectroscopy can be used for imaging vibrational wavefunctions of the ionized-excited helium dimer.