Differential Description of Multiple Ionization of Uracil by 3.5 MeV/u C6+ Impact
Round 1
Reviewer 1 Report
The authors present the results of a theoretical study on multi ionization of the biomolecule uracil. In a straightforward extension of previous work (ref. 22), they now present a very detailed differential analysis and discussion of double and triple ionization processes. The manuscript is well written and structured. Where possible, comparison is made to available experimental data, which are scarce, and the present results call for more differential experimental studies. I could recommend publication of the manuscript as it stands, however, I wish to invite the authors to briefly comment (give their personal viewpoint) on the question: "are multiply differential cross sections really needed in applications such as ion irradiation induced RNA and DNA damage (e.g. ion beam therapy, cosmic ray effects to passengers of airplanes and spacecraft, effects of radioactive exposure etc.)?".
Author Response
REFEREE 1:
The authors present the results of a theoretical study on multi ionization of the biomolecule uracil.
In a straightforward extension of previous work (ref. 22), they now present a very detailed
differential analysis and discussion of double and triple ionization processes. The manuscript is well
written and structured. Where possible, comparison is made to available experimental data, which
are scarce, and the present results call for more differential experimental studies. I could
recommend publication of the manuscript as it stands, however, I wish to invite the authors to
briefly comment (give their personal viewpoint) on the question: "are multiply differential cross
sections really needed in applications such as ion irradiation induced RNA and DNA damage (e.g.
ion beam therapy, cosmic ray effects to passengers of airplanes and spacecraft, effects of radioactive
exposure etc.)?".
We thank the referee for the careful reading of our manuscript. Following the referee’s suggestion,
we have introduced a comment in the introduction regarding the role of multiple differential cross
sections in track structure codes, together with a new reference (Liamsuwan and Nikjoo PMB 58,
673 (2013)). We have also reinforced the point in the conclusions section.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is interesting work. N-particle CTMC is very capable of describing multi-electron correlations, even if the framework is not so different from an independent-particle model, since the electron-electron interaction cannot be fully implemented in a classical-trajectory method (auto-ionization would occur).
Let me start with a few problems, though:
1) the special issue is about electron-impact collisions; the present work is about heavy-ion impact.
2) the title has already serious grammatical mistakes in it.
It should be multiple ionization (without article 'the'), and then not 'for of uracil', but just 'of uracil'. The term 'the multiple ionization' is used throughout, and it is not correct in English.
The main conclusion of the paper is about double ionization, and the relative electron distribution of the two ionized electrons. This is interesting and justifies publication in Atoms.
The main CTMC methodology has been explained in a recent article in Physical Review A (Ref. 22), and the present work expands on that work by looking at differential electron emission in double-ionization events.
The present approach is not exact by any means (even at the level of replacing quantum dynamics for electron motion by classical dynamics). The electron-electron interaction cannot be included properly due to the danger of auto-ionization. The instability of the (semi-)classical helium atom, e.g., has been used to promote quantum mechanics in its early days! Nevertheless, the present approach is described adequately as far as its limitations are concerned, and is very likely the best one can do in the context of heavy-ion collisions from a complicated multi-electron target, such as uracil.
The paper focuses on the distribution over polar angles of electrons emerging in a double-ionization process. It highlights the results in the form of a Dalitz plot (Fig.4).
It then moves on to triple ionization. Qualitative differences are found and described compared to double ionization. The conclusions appear to be logical, and I have no reservations as far as publication of this paper is concerned.
After being a bit shocked about the language error in the title, I was relieved to observe that most of the text is actually reasonably well written.
Author Response
REFEREE 2:
This is interesting work. N-particle CTMC is very capable of describing multi-electron correlations,
even if the framework is not so different from an independent-particle model, since the electron-
electron interaction cannot be fully implemented in a classical-trajectory method (auto-ionization
would occur).
Let me start with a few problems, though:
1) the special issue is about electron-impact collisions; the present work is about heavy-ion impact.
2) the title has already serious grammatical mistakes in it.
It should be multiple ionization (without article 'the'), and then not 'for of uracil', but just 'of uracil'.
The term 'the multiple ionization' is used throughout, and it is not correct in English.
The main conclusion of the paper is about double ionization, and the relative electron distribution
of the two ionized electrons. This is interesting and justifies publication in Atoms.
The main CTMC methodology has been explained in a recent article in Physical Review A (Ref.
22), and the present work expands on that work by looking at differential electron emission in
double-ionization events.
The present approach is not exact by any means (even at the level of replacing quantum dynamics
for electron motion by classical dynamics). The electron-electron interaction cannot be included
properly due to the danger of auto-ionization. The instability of the (semi-)classical helium atom,
e.g., has been used to promote quantum mechanics in its early days! Nevertheless, the present
approach is described adequately as far as its limitations are concerned, and is very likely the best
one can do in the context of heavy-ion collisions from a complicated multi-electron target, such as
uracil.
The paper focuses on the distribution over polar angles of electrons emerging in a double-ionization
process. It highlights the results in the form of a Dalitz plot (Fig.4).It then moves on to triple ionization. Qualitative differences are found and described compared to
double ionization. The conclusions appear to be logical, and I have no reservations as far as
publication of this paper is concerned.
After being a bit shocked about the language error in the title, I was relieved to observe that most of
the text is actually reasonably well written.
We thank the referee for the careful reading.
Having noticed that several ion-impact papers were already published in this issue, we asked the
Editor who invited us to submit the present manuscript. We therefore understand that the issue deals
with the interaction of electrons with atoms , molecules and surfaces at any stage of the collision. In
our particular case, and as the referee has already noticed, focus is made on a more representative
description of the interaction of the electrons with the target atom/ion along the whole collision
process.
We have corrected the typo indicated in the title and performed a careful inspection of our
manuscript.
Author Response File: Author Response.pdf
