Oscillatory patterns in angular differential ion-atom charge exchange cross sections: The role of electron saddle swaps

Abstract

Abstract. In this work, we have performed an experimental/theoretical study of state selective charge exchange cross sections in 1-10 keV/amu Ne 8+ +Na(3s) collisions. Theoretical calculations provided by the classical trajectory Monte Carlo method (CTMC) are contrasted to data obtained at KVI by means of the magneto-optical trap recoil-ion momentum spectroscopy technique (MOTRIMS). We find that for electron capture to n 10, a two-step mechanism which involves an initial electronic excitation followed by electron capture at a later stage of the collision applies. Oscillatory structures in the n-state selective capture cross sections and recoil ion transverse momentum distributions are present in the experimental data as well as in the theoretical results, and are ascribed to the number of swaps the electron undergoes across the potential energy saddle during the collision process.

Extension of CTMC Calculations to Multielectron Systems

“…One of the benchmark systems is He 2+ + Na (3 s), which was extensively studied experimentally and theoretically. In particular, one electron capture and ionization were analysed using the CTMC model, using oneelectron model potentials [10,11]. Figures 5.…”

“…The main reason, according to the authors, resided in the fact that the classical method is expected to better reproduce high n contributions since they start to reach their classical limit. Experimental and theoretical studies of partial cross sections were also performed at low energies for Ne 8+ + Na (3s) collisions [11], in order to get evidence for oscillatory structures in the energy distributions of the n-state cross sections. As seen previously, these oscillatory structures could be interpreted classically in terms of swaps the active electron undergoes across the potential saddle before it is captured by the projectile.…”

Recoil-ion momentum spectroscopy for cold rubidium in a strong femtosecond laser field

“…While most MOTRIMS setups are dedicated to ion-atom collision studies [33,34,[38][39][40][41][42][43], applications for studying the behavior of atoms inside fast strong laser fields are less common [44][45][46]. In this study, we develop a new MOTRIMS apparatus, aiming at studies of the ionization of rubidium (Rb) atoms in an ultrashort (35-100 fs), strong laser field (10 9 -10 16 W/cm 2 ) with wavelengths in the infrared regime and even with X-ray free-electron laser (FEL) fields in the future.…”