Interpretation of x-ray spectra emitted by Ar ions in an electron-cyclotron resonance ion source

Abstract

We examine the most important processes leading to the creation of excited states from the ground configurations of Ar8+ to Ar16+ ions in an electron-cyclotron resonance ion source, which lead to the emission of K x-ray lines. Theoretical values for inner-shell excitation and ionization cross sections, including double KL ionization, transition probabilities and energies for the de-excitation processes, are calculated in the framework of the multi-configuration Dirac-Fock method. With reasonable assumptions about the electron energy distribution, a theoretical Kα x-ray spectrum is obtained, which reproduces very closely a recent experimental result.

X-ray-spectroscopy analysis of electron-cyclotron-resonance ion-source plasmas

“…This method is an improvement of the method described in Ref. [22], that takes into account a more realistic electron energy distribution and the triple ionization by electron impact.…”

“…Considering the processes leading to an ion in the charge state q with a K hole and in the excited level i, the balance equation can be written as (22) where A q i is the level i decay probability by any process (radiative and radiationless), N q 0 is the q charge-state ion density in the ground configuration. In the same equation, σ K-exc,q i is the excitation cross section for the processes leading from an ion in the charge state q in the ground configuration to the excited level i of the same ion with a K hole, and σ…”

“…(22). All possible excitation, mono-, double-, and tripleionization processes leading, from the ground configuration of ions with two to seven electrons to excited states of ions with two to four electrons, with a K hole, as well as the de-excitation processes of the latter ones, are illustrated schematically in Fig.…”

“…In 2001, the present authors [22] performed a detailed analysis of K x-ray spectra emitted by Ar ions in an ECRIS plasma as reported in Ref. [4].…”

A vacuum double-crystal spectrometer for reference-free X-ray spectroscopy of highly charged ions

“…One consequence of the ion creation and excited level population mechanisms described in Refs. Costa et al (2001); Martins et al (2001Martins et al ( , 2009Santos et al (2010Santos et al ( , 2008Santos et al ( , 2011 is that the 1s2s 3 S 1 level in He-like ions is strongly populated. It is created by ionization of the Li-like ion ground state 1s 2 2s.…”