Electron-ion collisions: Dielectronic recombination and ionization

Abstract

Inelastic electron-ion collisions have been studied by using crossed-beam techniques. The effects of state mixing by extrinsic fields in the collision region were investigated for the dielectronic recombination process Mg +(3s) + e → Mg(3p, nl) → Mg(3s, nl) + hν. By field ionization of the Rydberg atoms produced, cross sections σ( n) have been measured. The observed large changes of σ( n) with alteration of the extrinsic field provided the first incontrovertible experimental evidence that dielectronic recombination can be changed by external fields. Absolute cross sections for electron impact single, double and triple ionization of singly and multiply charged krypton ions were measured. The energy ranged from below threshold up to 1000 eV. The influence of metastable states on the cross sections for single ionization is discussed. Contributions of inner-shell ionization with subsequent auto-ionization to double and triple ionization are identified. Connections between the three principal inelastic processes in electron-ion collisions, i.e. recombination, excitation and ionization, are pointed out. The influence of these processes on plasma-modeling calculations is briefly discussed.