Interatomic Coulombic decay in ion-dimer collisions*

Free-electron production is an exceedingly rare process in low-energy ion-atom and ion-molecule collisions. This may change if the target monomer is replaced by a dimer (or a larger cluster) which allows for interatomic Coulombic decay (ICD), i.e., the transfer of enough excitation energy from one constituent to a neighbor so that an electron can be released from the latter.

ICD in neon dimers impacted by slow ions has recently been observed at CIMAP/GANIL and semi-quantitatively explained by a classical over-the-barrier model calculation [1]. Using an independent-atom independent-electron model and a quantum-mechanical description of the electron dynamics we were able to confirm the occurrence of ICD in 2.81 keV/amu O$^{3+}$-Ne$_2$ collisions after capture of an inner-valence ($2s$) electron. We also showed that Li$^{3+}$ ions are far less efficient in initiating ICD in neon dimers because the energy level structure of these projectiles makes $2s$ capture unlikely [2]. 

Conversely, more recent calculations suggest that low-energy He$^{2+}$ ions are \textit{very} efficient ICD initiators, i.e., give rise to substantial low-energy electron emission from neon dimers in a regime in which continuum electrons are virtually nonexistent in the corresponding ion-atom collision [3]. In this talk, I will explain the main features and the limitations of our model, provide an overview of the results obtained, and discuss their implications.

[1] W. Iskandar et al., Phys. Rev. Lett 114, 033201 (2015)

[2] D. Bhattacharya and T. Kirchner, Phys. Rev. A 102, 062816 (2020)

[3] T. Kirchner, J. Phys. B 54, 205201 (2021)