Coulomb over-the-barrier Monte Carlo simulation for investigation of ion-dimer collision dynamics

What is it about?

We present a combined theoretical and experimental study of collision mechanisms involving low energy ions and van der Waals dimer targets. A classical calculation based on the Coulomb Over-the-Barrier Model has been developed in order to get access to primary and post collision mechanisms related to the dimers. A COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS) was employed to measure experimentally in coincidence the 3D momenta of the emitted ions. Four collision systems are used for this study involving Ar9+ and Xe20+ projectiles at 15 qkeV colliding with argon dimer and neon dimer targets. The model predictions are found in very good agreement with the experimental results, both for the relative yields of the different relaxation processes and for the associated transverse momentum exchange between the projectile and the target.

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Why is it important?

The investigation of primary and post-collision mechanisms involving van der Waals dimer targets raises new questions. For example, what is the role of valence electrons in dimers compared to covalent diatomic molecules? Does that lead to different behaviors in term of fragmentation channel cross section, scattering direction of the projectile, and relaxation processes? In this paper, we go deeper in answering those questions.