Direct observation of interatomic Coulombic decay and subsequent ion-atom scattering in helium nanodroplets

TL;DR

This study experimentally observes interatomic Coulombic decay in helium nanodroplets and investigates the subsequent ion-atom scattering, revealing energy loss mechanisms of ions within the cluster.

Contribution

First direct observation of ICD in helium nanoclusters and analysis of ion scattering dynamics inside the neutral cluster.

Findings

ICD occurs in helium nanoclusters with mean sizes 5000-30000.

Energetic He+ fragments undergo single binary collisions inside the cluster.

Energy loss of ions is primarily due to hard binary collisions.

Abstract

We report on the experimental observation of interatomic Coulombic decay (ICD) in pure $^4$He nanoclusters of mean sizes between $N \approx$ 5000 and 30000 and the subsequent scattering of energetic He$^+$ fragments inside the neutral cluster by using cold target recoil ion momentum spectroscopy. ICD is induced in He clusters by using vacuum ultraviolet light of $h\nu =$ 67 eV from the BESSY II synchrotron. The electronic decay creates two neighboring ions in the cluster at a well-defined distance. The measured fragment energies and angular correlations show that a main energy loss mechanism of these ions inside the cluster is a single hard binary collision with one atom of the cluster.