Theoretical study of the I++I− mutual neutralization reaction

Abstract

We have computed the cross sections of the mutual neutralization reaction between ${\mathrm{I}}^{+}$ and ${\mathrm{I}}^{\ensuremath{-}}$ for a collision energy varying from 0.001 eV to 50 eV. These cross sections were obtained using the adiabatic potential energy curves of the ${\mathrm{I}}_{2}$ system computed with a direct relativistic multireference configuration interaction method and a semiclassical approach (i.e., Landau-Zener surface hopping). We report the cross sections towards the following neutral states: $\text{I}(^{2}P_{3/2})+\text{I}{(}^{2}{P}_{3/2})$, $\text{I}{(}^{2}{P}_{3/2})+\text{I}{(}^{2}{P}_{1/2})$, $\text{I}{(}^{2}{P}_{1/2})+\text{I}{(}^{2}{P}_{1/2})$, and $\text{I}(5{p}^{4}6s)+\text{I}{(}^{2}{P}_{3/2})$. We also discuss the cross sections towards the following two excited ionic states: ${\text{I}}^{\ensuremath{-}}{(}^{1}{S}_{0})+{\text{I}}^{+}{(}^{3}{P}_{0})$ and ${\text{I}}^{\ensuremath{-}}{(}^{1}{S}_{0})+{\text{I}}^{+}{(}^{3}{D}_{2})$. The results of these calculations are in qualitative accordance with recent experimental measurements conducted in the Double ElectroStatic Ion Ring ExpEriment (DESIREE) in Stockholm. These results can be used to model iodine plasma kinetics and thus to improve our understanding of the latter.