Investigations of Electron Dynamics in Ion-Dimer Collisions that Facilitate Interatomic Coulombic Decay

Abstract

In the field of atomic physics, there have been developments and investigations into emergent processes in clusters. One specific process that has gained interest in recent times is called interatomic (or intermolecular) Coulombic decay (ICD). ICD is a rapid decay mechanism in which electron removal from one atom in an excited ionic state triggers low-energy electron emission from a neighbouring atom, leading to cluster fragmentation. These low-energy electrons are of significant applied interest due to their ability to break molecular bonds and damage biological matter, with relevance to cancer radiotherapy. To study ICD, theoretical models were developed to describe ion-cluster collisions using a simplified time-dependent Hartree-Fock approximation and the two-centre basis generator method, with many-body quantum-mechanical challenges addressed through the independent atom and independent electron models. Statistical analyses — including a combinatoric multinomial probability method and a determinantal method using inclusive probabilities — were employed to study the electron dynamics that precede cluster fragmentation. Results indicate that ICD is highly efficient for single 2s electron removal in a neon dimer target with a He⁺ projectile, and for single 3p electron removal with simultaneous 3p excitation in an argon dimer target, with strong agreement observed across all analytical approaches.