Double ionization of atomic cadmium

Abstract

We have recorded the double photoionization spectrum of atomic Cd at four different photon energies in the range 40-200 eV. The main channel is single ionization and subsequent decay of excited Cd + states, some involving Coster-Kronig processes, whereas direct double ionization is found to be weak. The decay of the excited Cd + states shows a strong selectivity, related to the configuration of the final state. Double ionization leading to the Cd 2+ ground state is investigated in some detail and is found to proceed mainly through ionization and decay of 4d correlation satellites. The most prominent autoionization peaks have been identified with the aid of quantum-mechanical calculations.

Triple ionization of atomic Cd involving4p−1and4s−1inner-shell holes

“…However, since the energy of all 4d 8 5s 2 states is below the ground-state energy of Cd 3+ , channel (6) can also be excluded. Our calculations also showed that some 4d 8 5s6s states have energies above the ground state energy of Cd 3+ , which agrees with previous findings in the study on double ionization [13]. We therefore also included several shakeup transitions in our computations, as discussed in following subsection.…”

“…In using 200 eV photon energy, the removal of either a 4p or a 4s electron, both with additional shakeup processes during the photoionization is possible. Since this is the same photon energy as previously used for analyzing the double ionization spectrum of Cd [13], the present study can be regarded as a direct extension of that previous work. In adjusting the radiation intensity to a level which implied low ionization event probability per light pulse, the present experimental data were obtained in classical coincidence conditions.…”

“…[8]). Also a recent Auger-electron photoelectron coincidence spectroscopy study of doubly ionized Cd found that the 4p −1 hole states preferably decay in form of 4p −1 → 4d −2 transitions [13]. In the same study, features in the double ionization spectra were observed at the binding energies 60-68 eV and were found to belong predominantly to the levels of the 4d 8 nl,n l configurations [13].…”

“…Ref. [13]. However, since the energy of all 4d 8 5s 2 states is below the ground-state energy of Cd 3+ , channel (6) can also be excluded.…”

“…5 in Ref. [13]), where it was mentioned that the 4p −1 4d −1 states are likely to decay very rapidly in the form of 4p −1 4d −1 → 4d −3 GCK transitions (see Refs. [23,24] Fig.…”