Fully relativistic R-matrix study of the interaction between a slow electron and atomic iodine: Scattering and photodetachment

An 11-state close-coupling calculation for the interaction between a slow electron and atomic iodine is carried out using the fully relativistic R-matrix method. The cross sections are presented for the photodetachment of a negative atomic iodine ion and for electron scattering by neutral atomic iodine from the threshold to 8 eV. The electron affinity for negative iodine is obtained as 2.958 eV. For the photodetachment process, we get fairly good agreement with experimental results for the distinct spin-orbit split between the 5p3/2 and 5p1/2 thresholds due to the relativistic effect as well as for the cross sections near the thresholds. The electron scattering cross sections display energy dependence similar to that for electron scattering by heavy rare-gas atoms, i.e., a Ramsauer-Townsend minimum well at a lower energy and a broad peak after the well