Large Negative-Ion Formation in Grazing Scattering of Neutral Carbon Atoms from a CsI(100) Surface

Abstract

Negative ions are crucial in various scientific and technological fields, such as antimatter research, interstellar chemistry, accelerator-based radionuclide dating, fusion injection for controlled nuclear fusion, and neurological disease treatment. Thus, producing a large number of negative ions is highly important. Herein, we present the first theoretical evidence of a large fraction of negative-ion formation during the grazing scattering of carbon atoms from a CsI(100) surface. The conversion efficiency of the negative ions reaches ≥86% within a projectile energy range of E_p ∈ [5,10] keV. These remarkable results are attributed to large anion and cation polarizations, which lead to an evidently large Mott–Littleton polarization interaction. This interaction lowers the energy defect of valence band electron capture to below 1.8 eV near the surface anion sites, drastically increasing the electron-capture probability. The destruction of negative ions occurs owing to affinity electron detachment via the Coulomb barrier tunneling to the vacuum level during the interactions with surface anion sites along their trajectories. Our results indicate that this collision system can be used to design next-generation negative carbon ion sources for studying the isotope shift of electron affinity and provide insights into electron correlation effects and molecular-level irradiation pathological studies, especially for promoting nerve tissue repair and regeneration through E_p ∈ [5,10] keV negative carbon ion irradiation.