Scattering of e± from CF3I Molecule
, M. Mousumi Khatun 1,2, M. Masum Billah 1, M. M. Haque 1, Hiroshi Watabe 3, A. K. Fazlul Haque 1,3,* and M. Alfaz Uddin 1
Round 1
Reviewer 1 Report
In the article “Scattering of e± from CF3I molecule” Khandker et al. have evaluated theoretically cross sections for several processes taking place in collisions of the CF3I molecule with electrons and positrons. The majority of the data presented are on elastic scattering. Also, integrated total, integrated total ionization, momentum transfer, and viscosity cross sections were computed.
The theoretical approach to compute the cross sections is based on a numerical solution of the relativistic Dirac equation, which provides scattering amplitudes. The scattering amplitudes are used to evaluate differential and integrated cross sections. The potential of interaction between the molecule and electron (or positron) is based on the independent atom model (IAM), which is appropriate for large scattering energies (maybe, above 20eV).
The obtained results and the developed theoretical methods present a significant interest for the corresponding communities. Th article is clearly written and I would enthusiastically recommend it for a publication in Atoms.
I do have a few questions and suggestions for small additions to the text.
How sigma_{bc} in Eq.(15) is obtained? What is its meaning?
The ionization cross section is computed using the ratio parameter Eqs. (38),(39). Can the authors add some discussion about evaluating the ionization cross section in this way? What is the theory behind the idea?
Is there way to adapt the theory to compute cross sections for some other inelastic processes, such as excitation, ionization to specific electronic states, dissociation? I suppose it is not easy, but the authors may want to write a few words about it in the discussion/conclusion section. It is an interesting and important topic, especially because of the motivation of the present study: modeling the technological plasma. For the modeling cross sections for individual inelastic processes are needed.
There are several empiric parameters in the theory. What is the uncertainty of the obtained cross sections with respect to uncertainties of the parameters? Can the authors assess the uncertainty of the obtained cross sections? Without an assessment of uncertainty, it is difficult to judge how accurate the present calculations are.
Has this model been tested on other targets, for which extensive theoretical data exist, such as H2, H2O, N2, or other molecules? It would good to know how well the model performs for these benchmark molecules.
Author Response
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Reviewer 2 Report
The article is devoted to the complex and interesting problem of electron (and positron) scattering by complex molecules. At the same time, the lack of experimental data stimulates theoretical searches in this direction.
To overcome the difficulties caused by the many-particle nature of these processes, the authors propose to treat the problem in terms of the independent atom approximation (IAM), supplemented by a screening correction (SCIAM) in the case of low energies of the incident particle. In turn, to solve the problem of an electron scattering by constituent atoms, the authors resort to ELSCATM code based on the Dirac equation (using the partial wave decomposition).
From a comparison of the results obtained in the article for the scattering of an electron by a trifluoroiodomethane molecule with the experiment and calculations of other authors, it can be concluded that the chosen approach makes it possible to reasonably describe the dynamics of the process.
On the other hand, in my opinion, the authors should verify the convergence of the partial expansion of the scattering amplitudes in the high-energy case…
Author Response
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Reviewer 3 Report
Dear Editor,
The work addresses the theoretical investigation of the electron and positron scattering from CF3I molecule over a wide energy range using the Dirac partial wave methodology. The results from the present theory such as DCS, TCS etc are compared with experimental and available theoretical results. Although the independent atom model(IAM) and the screened IAM approaches seem simple ones, the agreement with the experiment and ab-initio theoretical results convince the reader regarding the suitability and robustness of the methods. I find the description of the theory and result presentation suited for publishing in Atoms. Hence I recommend for publication. However, there are a few points that require attention and revision. The specific points are addressed below
(1) In line number 173, MCHF is mentioned. The description being completely relativistic, the use of non-relativistic MCHF for obtaining the ground state wavefunction is questionable. This could be a typo as well, which can be corrected. Besides, have the authors used multi-configuration initial state? If so, the configuration details can be added for each atom considered.
(2) A remark on number of partial waves required for convergence would be suitable to add in the theory /results section.
(3) While comparing the present results with other theory works, it is important to mention the level of theories other authors used, against which the results are compared. I find that the particular mention is also not complete in the introduction section. The authors can give a description of other theories against which the present results are compared. This could be done when the particular figures are discussed.
For being very specific, concerning Figure 1, it is crucial to specify at what levels theoretical results of Ref 30 and 27 are accomplished. SImilarly in other figures also.
(4) Certain disagreements of the present results with ab-initio calculation are reported. The authors may explain the merit of the higher level of theories. In other words, why the disagreement exists in the present results, could be elaborated. For instance, the reason for missing minimum in Figure 1 could be due to not having an adequate number of partial waves in SCIAM formalism. Such details can be elaborated.
(5)Showing the effective normalized charge density (Rho) can be considered.
(6) In line numbers 328 - 334, the reason behind the agreement of IAM and SCIAM results are high-energy is discussed. From an alternative angle, authors can additionally include the probe time differences in both cases. For example, in low-energy scattering, the projectile gets enough time to scan the features of the target, and hence IAM and SCIAM differ. On the contrary, at high energies, the projectile just sweeps through without paying attention to the details. This alternate viewpoint can also be added.
(7) In Figures 6 and 7, the Sherman function is presented, but has not shared the implications of the features of the curve. It is important to discuss in detail the implications of the shape of the function at various angles.
(8) Are there resonances in the scattering cross-section? If so, a discussion on the scattering resonance can be presented when discussing the total cross-section.
Author Response
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