Theoretical electron-impact-ionization cross section for Fe11+forming Fe12+

Abstract

We have calculated cross sections for electron impact ionization (EII) of P-like Fe 11+ forming Si-like Fe 12+ . We have used the flexible atomic code (FAC) and a distorted-wave (DW) approximation. Particular attention has been paid to the ionization through the 3l → nl and 2l → nl excitation autoionization (EA) channels. We compare our results to previously published FAC DW results and recent experimental results. We find that the previous discrepancy between theory and experiment at the EII threshold can be accounted for by the 3l → nl EA channels which were not included in the earlier calculations. At higher energies the discrepancy previously seen between theory and experiment for the magnitude of the 2l → nl (n 4) EA remains, though the difference has been reduced by our newer results. The resulting Maxwellian rate coefficient derived from our calculations lies within 11% of the experimentally derived rate coefficient in the temperature range where Fe 11+ forms in collisional ionization equilibrium.

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

“…4) suggests that 2p → n ′ l ′ EA cross sections with n ′ ≥ 4 are almost insignificant, in contrast to the theoretical predictions. This situation is similar to what has been seen by us in other iron M-shell ions [52][53][54][55] and has also been investigated and discussed in more detail by Kwon and Savin [56] for EII of Fe 11+ .…”

“…Since we have normalized the present PR and EII rate coefficients to our previous results the same uncertainty applies here. It should be pointed out, that the normalization could be carried out unambiguously, since there was no visible difference -apart from differences due to different experimental energy spreads -between the previously measured DR resonance structure of 56 Fe 14+ and the present one for 57 Fe 14+ . The 6% estimate for the 3s 3p 3 P 0 fraction was based on assuming initial statistical populations of the 3 P J levels.…”

“…If such resonances could be observed for 56 Fe 14+ their presence in the 57 Fe 14+ DR spectrum would be exponentially suppressed with time elapsing after injection into the storage ring, i.e., with the 3s 3p 3 P 0 level decaying via the hyperfine-induced transition. However, no significant differences between the measured DR resonance structure of 56 Fe 14+ and 57 Fe 14+ were found. This is attributed to the fact that DR resonances of 3 P 0 parent ions have been predicted to be only weak and to be blended with the rich DR resonance structure of 1 S 0 ground-state parent ions [11].…”

Electron-impact single ionizaiton for W 4+ and W 5+

“…The BR for autoionization of level j by emission of a single electron can be expressed as [29] B a j =…”

The Strong Enhancement of Electron-Impact Ionization Processes in Dense Plasma by Transient Spatial Localization

“…To date, most atomic data on electron–ion collisional ionization have been obtained for isolated atoms or ions [ 7 , 12 , 13 , 14 ], where the coupling with the plasma environment was assumed to be trivial and was thus neglected. However, these data are only applicable to rarefied plasmas, for which there is, in general, a reasonable agreement between experimental and theoretical cross sections due to the adequate consideration of physical effects, such as by including enough excitation auto-ionization channels in the calculations [ 15 , 16 ]. If the plasma density is sufficiently high and the coupling cannot be neglected, plasma screening plays a non-negligible role and should be considered when determining the electronic structure.…”