Negative Ion Conversion by Neutral Carbon Atoms Grazing Scattering from the KI(100) Surface.

In this work, we performed a theoretical calculation of the negative ion conversion by a neutral carbon atom beam grazing scattering from the KI(100) surface. The Madelung potential, image potential, and ML-polarization interaction contributions are included in the calculation of the electron capture energy defect of the valence band near surface anion sites along the projectile incidence direction. The loss of the formed negative ions does not originate from the electron loss to the unoccupied conduction band or neutral exciton states but results from the Coulomb barrier tunneling detachment of the loosely bound affinity electron to the vacuum level during the interaction with surface lattice anion sites. Here, the large fraction of negative-ion conversion (≥50%) within the projectile energy range of E_p ∈ [5.7,14.9] keV implies the present collision system could be directly used to design the next-generation negative carbon ion sources for the study of isotope shifts in electron affinity, electron correlation effects and for the promotion of nerve tissue repair and regeneration by negative carbon ion irradiation.