Shake-Off Process in Non-Sequential Single-Photon Double Ionization of Closed-Shell Atomic Targets
Round 1
Reviewer 1 Report
This paper is interesting and makes a nice contribution to the Special Issue for Professor Amusia.
However the paper could benefit from a careful reading as there are a few obvious minor errors and a few places where some clarity would help the manuscript. After these are addressed (see below), the paper can be accepted for publication.
The paper presents as its main results the single differential cross section. However the triple differential (angular resolved) cross section is more commonly measured. Can the current approach give good results for this quantity?
In the introduction one attosecond is stated as 1e-16s. This surely should be 1e-18 seconds and should be corrected.
Concerning figure 3: what about Be (1s) and Ne (1s) time delay. Will it be shorter than (say) helium? Or loner since the increased nuclear charge will be more of an effect. Might be interesting to study?
Some typos/mistakes:
3 lines before end of Section 1: access -> excess
Section 3.1, first line: suit -> suite
1st line of page 4; stript -> strip
Before equation 5: correspoding -> corresponding
Last line of page 5: nealry -> nearly
Section 4: singificant -> significant
References 9,17 are incomplete and need the full citation.
Author Response
The author wishes to thank the reviewer for a thorough reading of the manuscript and many helpful comments and suggestions.
In the following, the author clarifies several points raised by the referee and indicates the changes that are made to address these points where necessary. The Q&A style is adopted for clarity.
Q1. The paper presents as its main results the single differential cross section. However the triple differential (angular resolved) cross section is more commonly measured. Can the current approach give good results for this quantity?
A1. The referee is correct and triply differential cross-sections (TDCS) are generally more informative in PDI than singly differential cross-sections (SDCS) . However, for slow shake-off electrons, the angular distribution is generally isotropic (see e.g. Ref. [7]) and thus TDCS carries little additional information. This comment is already made in line #121.
Q2. In the introduction one attosecond is stated as 1e-16s. This surely should be 1e-18 seconds and should be corrected.
A2. This is a very helpful suggestion that saved the author from an embarrassing mistake.
Q3 Concerning figure 3: what about Be (1s) and Ne (1s) time delay. Will it be shorter than (say) helium? Or loner since the increased nuclear charge will be more of an effect. Might be interesting to study?
A3 The case of Be(1s) was investigated, the associated time delay was found an order of magnitude smaller than Be(2s) for an obvious reason: the Coulomb field of the bare nucleus makes all the correlations and associated time delay negligible. This fact is commented in the revised manuscript
All the typographic errors and bibliography omissions are acknowledged and corrected.
Reviewer 2 Report
Referee Report
The paper presented by A. Kheifets, one of the pupils of Miron Amusia, is devoted to the theoretical consideration of the shake-off process in the non-sequential double photoionization (DPI). The differential and total cross sections are calculated for a number of atoms. The calculations have been made using Green’s function method. The most interesting part is a calculation of the time-delay in DPI for several intra-shell and inter-shell shake-off transitions. The paper is clearly written, contains necessary references. The results are new and interesting for further theoretical and experimental investigation of DPI. I recommend the paper for publication with minor corrections listed below.
Section “1.Introduction”, line 34, correct “1 as = 10^-18 s”.
Section “3.3. Time-delay”, line 135, correct “inter-shell SO”.
Section “4. Summary and outlook”, line 151, correct “inter-shell SO”.
Author Response
The author wishes to thank the reviewer for their positive evaluation of the present work.
All the typographic errors marked by the assessor are corrected in the revision.
Reviewer 3 Report
This is an excellent paper and a fitting tribute to Miron Amusia. There are several (relatively minor) points that the author should look at prior to publication. Specifically:
1. Line 70: neither -> nor.
2. Please define the symbol, "delta" on the RHS of Eq. (1). Does it have a definite value, or is theis to be understood as the limit as "delta" -> 0?
3. The equation on the second line of page 4 either has something missing or needs more explanation. I didn't understand it.
4. In the caption for Fig. 2, there is talk of the experiment being normalized. Is this does because the experiment is a relative experiment? Or are the magnitudes of theory and experiment different? In either case this normalization should be commented on or, particularly if there are magnitude differences, explained.
5. If I understood this paper correctly, the knock-out "mechanism" dominates near the DPI threshold. If that is true, what is the point, in Fig. 3, or showing the time delay near threshold? Perhaps I'm missing something here.
6. In Fig. 3, the horizontal axis is photoelectron energy. Since there are two electrons in DPI is this the total energy of the two electrons? The energy of the faster electron? Or what? Please explain.
7. A comment on how these time delays compare with the single photoionization time delay at the same photon energy. Are the DPI delays always larger? Some comments here would be useful.
Author Response
The author is really pleased with a high assessment of his work.
All the trivial corrections and suggestions made by the referee are accepted and taken care of in the revision.
The following points need more attention.
Q1: Line 70: neither -> nor.
A1: Accepted
Q2: Please define the symbol, "delta" on the RHS of Eq. (1). Does it have a definite value, or is theis to be understood as the limit as "delta" -> 0?
A2: The infinitesimally small δ → 0 in the energy denominator defines the pole bypass.
Q3: The equation on the second line of page 4 either has something missing or needs more explanation. I didn't understand it.
A3: The corrected equation reads ε = Ef-ω<0
Q4: In the caption for Fig. 2, there is talk of the experiment being normalized. Is this does because the experiment is a relative experiment? Or are the magnitudes of theory and experiment different? In either case this normalization should be commented on or, particularly if there are magnitude differences, explained.
A4: In all cases, the measurement was relative and the experiment was normalized to available theoretical data. This is now explained in the figure cation and the tect.
Q5: If I understood this paper correctly, the knock-out "mechanism" dominates near the DPI threshold. If that is true, what is the point, in Fig. 3, or showing the time delay near threshold? Perhaps I'm missing something here.
A5: The data of Fig. 3 refer to the case of very large photon energy which is all but taken by the fast primary photoelectron. The secondary SO electron takes very little of this energy. In this kinematics, the SO mechanism clearly dominates over KO. This note is added to the revised manuscript.
Q6: In Fig. 3, the horizontal axis is photoelectron energy. Since there are two electrons in DPI is this the total energy of the two electrons? The energy of the faster electron? Or what? Please explain.
A6: This question is answered in the previous point.
Q7: A comment on how these time delays compare with the single photoionization time delay at the same photon energy. Are the DPI delays always larger? Some comments here would be useful.
A7: The paragraph is added on time delay in single photoionization, see lines #172-179 in the revised manuscript.
