Cross Sections and Rate Coefficients for Vibrational Excitation of H2O by Electron Impact
, Maria Tudorovskaya 4 and Viatcheslav Kokoouline 5,*Round 1
Reviewer 1 Report
It is hard to overstate the importance of water in our environment, and thus the interest to investigate its fundamental properties and responses to external influences, such as by electron impact. Actually, water is the dominant greenhouse gas, but that is not important here.
Even fundamental molecules have not been fully studied experimentally. It is necessary to bridge the experimental data by computations (as done here), so that trends and generalities can be established for a framework of understanding.
Several of the authors have worked in the field since many years and displayed their expertise. I see no reason to doubt their competence. The high level of language competency is appreciated.
Line 67, replace "such" by "so"
Line 75, please explain the akronyms DZP and cc-pVTZ to the less initiated readers at the first occurrence
(not only as late as in line 97 for the latter)
Line 152: "sources" is plural, therefore replace "is" by "are"
Line 163: "So that" is un-English, maybe use "Consequently, "
Author Response
We have corrected the problems indicated by the referee.
Reviewer 2 Report
The authors presented calculation of fross sections for vibration (de-)excitation of water by an electron impact. They also calculated thermally-averaged rate coefficients in the interval from 10 to 10,000 K.
Besides the scientific significance related to method of calculation of cross sections for vibrational excitation, the calculated results for rate coefficients could be on help in modelling of non-LTE spectra of water in various astrophysical environments.
I have only minor question/comment:
I noticed your comparison for the bending mode where at energies above 4 eV, the present values are below by about 30% than the swarm data and by a factor of 2 than the recent experiment by Khakoo et al. Beam experiments are hard to performed and its errors could be up to 50%. The sworm data are more precisly, but often some other effect would be included and take influence to measurement.
Nevertheless, it seems to me that the experimental data indicate that the cross sections in this energy range should be larger. Therefore, I would like to ask you if you have thought of any resonant effect that could be included and improve your calculated results.
Author Response
Following referee's suggestion, at the end of Subsection 3.1, we have added a short discussion about the significant difference between experimental and theoretical results at energies around 4 eV. It is quite likely that the disagreement is due neglected (in all theoretical studies) excitation of vibrational resonances of the H2O- anion in this energy region. Similar resonant mechanism was observed in electron-impact vibrational excitation of CO and explained by Laporta et al. (2012).
