Charge transfer and ionization in collisions between atomic ions and rare-gas atoms for primary-ion energies below 100 eV

Cross sections for the production of Kr⁺, Kr⁺⁺, Xe⁺, and Xe⁺⁺ in collisions of H⁺, He⁺, and Ne⁺ with Kr and Xe have been measured for primary-ion kinetic energies E between 0.5 and 100 eV. These cross sections rise rather sharply as E is increased, reach a maximum, and then decrease rather slowly. Maximum values of the cross sections range from 0.1 to 40 Ų. Production of the doubly charged ions must correspond to the production of a free electron; these ionization processes have apparent threshold energies 0-4 eV above the true threshold energies. Collisions of H⁺ with Kr and Xe do not produce doubly charged positive ions. The cross sections for reactions that release a free electron are not adequately represented by any of the theoretical expressions with which the experimental data were compared. Cross sections for the production of singly charged positive ions are larger for the more complex target atoms and lighter primary ions; these cross sections are well represented by the charge-transfer theory of Rapp and Francis when the experimental cross sections are large, but not otherwise. Rapp and Francis's formulas are not applicable to charge-transfer reactions having small cross sections. The present experimental data agree fairly well with previous experimental results.