Investigations of electron removal processes in slow He$^{2+}$ and He$^{+}$-Ne$_2$ collisions indicate high Interatomic Coulombic Decay yield

Abstract

We implement an independent-atom and independent-electron model to investigate the collision systems of He$^{2+}$ and He$^{+}$ ion projectiles impinging on a neon dimer target. The dimer is set to be stationary at its equilibrium bond length with the projectile traveling parallel to the dimer axis at a speed corresponding to the collision energy of 10 keV/amu. Two approaches called multinomial and determinantal are used as an analysis of these collisions. Each of the analyses is broken down into two types of models that do not and do include a change in the projectile charge state due to electron capture from the dimer. All calculations are performed using both a frozen atomic target and a dynamic response model using the coupled-channel two-center basis generator method for orbital propagation. All one- and two- electron removal processes are calculated, though particular attention is paid to those that result in the Ne$^{+}$-Ne$^{+}$ fragmentation channel due to its association with interatomic Coulombic decay (ICD). We confirm in all analyses and models that Ne(2$s$) electron removal is strong so that ICD will contribute to dimer fragmentation as has been previously demonstrated. The model that takes into account the change in projectile charge state indicates that there is a pure ICD yield when utilizing a He$^{+}$ projectile.