Higher-Order Recombination Processes in Argon Ions Observed via X-ray Emission in an EBIT
, Pedro Amaro 2, Filipe Grilo 2 and Andrzej Warczak 1
on behalf of the SPARC Collaboration
Kouichi Soejima
Round 1
Reviewer 1 Report
The manuscript entitled 'Higher-order recombination processes in Argon ions observed via x-ray emission in an EBIT' by Weronika Biela-Nowaczyk et al. reports on DR and higher-order recombination processes in Argon ions observed via x-ray emission in an EBIT. With the aid of FAC calculations, the authors identified the observed different DR processes, i.e. KLL,KLM,KLN,KNO and KMM, and concluded that the resonant structures of KLL DR process is charge state dependent while others are charge state independent. An addition, the authors investigated the contribution of the intershell higher order recombination processes in observed spectra and found that for He-, Li-, and Be-like argon KLL DR process dominates over the higher-order recombination processes, while for B- and C-like argon ions the KL-LLL TR process is stronger than DR. Overall the paper is well written and the topic is very relevant to Atoms journal and to the whole community. It deserves therefore to be published after the authors have addressed the following suggestions/corrections/remarks.
1. The structure of the paper seems strange. In Section 2. Experimental methods and theoretical approach didn't include much discussion about the theoretical approach but the theoretical results. I would suggest the authors move the paragraph 3 and 4 to Section 3 and include more details about the calculations, for example, how they consider the configuration interaction in the initial, intermediate, and final states. The paper is ended with section 4. Discussion which is very strange because the content in Section 4 is more like the conclusion.
2. It is concluded that the resonant structures of KLL DR process is charge state dependent. It will be helpful if the authors draw a plot about this statement from their measurements and also compare the results with the their calculations?
3. There are some previous relevant studies about KLL resonance of, for example, He-, Li-, Be-, B- and C-like ions. Some authors have tried to derive the semiempirical Z-scaling law for DR resonance strengths as a function of the atomic number. Many of the measurements have been done for high-Z. In order to provide a more accurate scaling function and the fitting parameters, experiments in low-Z side are required. From this aspect, the measurements presented by the authors are needed. Could the authors gather the relevant results and complement their own results and update the scaling law? The relevant studies include (but not limited, the authors can check the references in these papers):
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.44.223
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.75.012702
https://iopscience.iop.org/article/10.1088/0953-4075/44/22/225203
https://iopscience.iop.org/article/10.1088/0256-307X/26/3/033401
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.81.022714
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.88.042704
https://aip.scitation.org/doi/10.1063/1.4948420
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.99.012506
4. How about the comparison between the calculated and measured DR/TR strengths? Could the authors provide a plot about the comparison?
5. From Figure 5, the calculated resonance strength seems in excellent agreement with the experimental results. In the text, the authors claimed:"Resonance strength axis of each group was scaled so that the maximal resonance strength lies on top of 101 experimental data resonant structure." Could the authors provide more information about how they do the scaling? Can they be compared with the measurements directly?
6. minor comment: Line 62-63, Page 3, (2100 - 3400) eV should be (2100 - 3400 eV)
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper is worthy of publication, containing useful information about higher order rearrangement of electrons in highly charged ions. The following minor corrections are needed. 1. line No.62 ;spelling error (on to one). 2. The content of the part marked "discussion" is the conclusion. So, I suggest section marked "Results" on line 84 be revised to "Results and Discussion" and "Discussion" on line 113 be revised to "Conclusion".
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
