Dielectronic Recombination of FexvForming Fexiv: Laboratory Measurements and Theoretical Calculations

Abstract

We have measured resonance strengths and energies for dielectronic recombination (DR) of Mg-like Fe xv forming Al-like Fe xiv via N ¼ 3 ! N 0 ¼ 3 core excitations in the electron-ion collision energy range 0Y45 eV. All measurements were carried out using the heavy-ion test storage ring at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We have also carried out new multiconfiguration Breit-Pauli (MCBP) calculations using the AUTOSTRUCTURE code. For electron-ion collision energies P25 eV we find poor agreement between our experimental and theoretical resonance energies and strengths. From 25 to 42 eV we find good agreement between the two for resonance energies. But in this energy range the theoretical resonance strengths are %31% larger than the experimental results. This is larger than our estimated total experimental uncertainty in this energy range of AE26% (at a 90% confidence level). Above 42 eV the difference in the shape between the calculated and measured 3s3p( 1 P 1 )nl DR series limit we attribute partly to the nl dependence of the detection probabilities of high Rydberg states in the experiment. We have used our measurements, supplemented by our AUTOSTRUCTURE calculations, to produce a Maxwellian-averaged 3 ! 3 DR rate coefficient for Fe xv forming Fe xiv. The resulting rate coefficient is estimated to be accurate to better than AE29% (at a 90% confidence level) for k B T e ! 1 eV. At temperatures of k B T e % 2:5Y15 eV, where Fe xv is predicted to form in photoionized plasmas, significant discrepancies are found between our experimentally derived rate coefficient and previously published theoretical results. Our new MCBP plasma rate coefficient is 19%Y28% smaller than our experimental results over this temperature range.

Absolute rate coefficients for photorecombination and electron-impact ionization of magnesiumlike iron ions from measurements at a heavy-ion storage ring

“…The present recombination measurements greatly extend the energy range of our earlier experimental PR results [11] which were limited to energies between 0 and 45 eV. To the best of our knowledge there are no previous * Stefan.Schippers@physik.uni-giessen.de experimental results available for EII of Fe 14+ .…”

“…Except for the results of our previous study of ∆N = 0 DR of Fe 14+ [11] there are no further experimental PR rate coefficients available for Mg-like ions. Theoretical calculations for this isoelectronic sequence of ions have been carried out by Altun et al [12] for ions with nuclear charges 13 ≤ Z ≤ 54.…”

“…The experimental procedures were similar to those applied in previous measurements [11,[30][31][32] (and references therein). Here we focus on the details that are specific to the present measurements.…”

“…For DR a distinction is made whether the core electron is excited within an atomic shell (∆N = 0 DR) or whether it is excited to the next higher shell (∆N = 1 DR). Our previous experiment [11] addressed only ∆N = 0 DR and TR. Here we additionally consider ∆N = 1 DR involving the excitation of a 2s, 2p, or 3s core electron.…”

Resonant Transfer Excitation of Fluorine-Like Mo33+ Ion

“…• By the same way, the RTEX cross sections for Lshell excitation are larger than for K-shell excitation by a factor of about 10 4 .…”