Investigations on Pressure Broadening Coefficients of NO Lines in the 1←0 Band for N2, CO2, Ar, H2, O2 and He
, Denghao Zhu 1, Bo Shu 1, Ravi Fernandes 1,2 and Zhechao Qu 1,*Round 1
Reviewer 1 Report
In this manuscript “Measurements of pressure broadening coefficients of NO lines in the 1-0 band for N2, CO2, Ar, H2, O2 and He”, authors reported CO2, N2, Ar, O2, H2, He and Air -induced pressure broadening coefficients based on a tunable diode laser absorption spectroscopy. Research methods are reasonable, some new experimental results were obtained, but lack of innovation and highlights to attract readers. The manuscript needs a major revision on this point.
1. Author reported many broadening coefficients in section 4.1 – 4.6, and compared with literature values in section 4.7, however, there lack some further discussion, such as what are the differences and similarities between the experimental results of different gas samples, and the significance of this series of studies.
2. In L149, “Within Peak 1 (Ω1/2) or Peak 2 (Ω3/2), the 10 NO lines have the same broadening coefficient”, what’s the “Ω1/2” and “Ω3/2” mean?
3. Table 1 list a lot of dates, but they are very close and the author does not give any further explanation. The necessity of Table 1 is questionable.
4. The authors should use high resolution figures for the manuscript, such as Figure 1(b), 2, 3, 4, and so on.
5. Some minor typography correction. In L44, a blue “s” in “about half of the total NO emissions”. In L101, the “Eq. Error! Reference source not found.” In L156, “Error! Reference source not found. (a) shows a subset of the measured line profiles for the NO/CO2 gas mixture at two pressures.” In L168, L174, and L178 all have similar errors.
Author Response
Response to the reviewer #1
Ms. Ref. No.: applsci-2137624
Title: Investigations on pressure broadening coefficients of NO lines in the 1←0 band for N2, CO2, Ar, H2, O2 and He
Dear Editor,
We thank the reviewers for their careful reading and helpful comments. In the following, we respond to the comments and indicate the changes made in the manuscript.
These changes are highlighted in yellow in the revised paper and will be explained below point by point in text highlighted in red, intertwined with the reviewers' remarks.
The revised manuscript is named as 'author-coverletter-25980000.v2.docx' in the attachment.
Reviewer #1: In this manuscript “Measurements of pressure broadening coefficients of NO lines in the 1-0 band for N2, CO2, Ar, H2, O2 and He”, authors reported CO2, N2, Ar, O2, H2, He and Air -induced pressure broadening coefficients based on a tunable diode laser absorption spectroscopy. Research methods are reasonable, some new experimental results were obtained, but lack of innovation and highlights to attract readers. The manuscript needs a major revision on this point.
We thank the reviewer for his/her general positive comments on our work! In general, the innovation and highlights of this work have been briefly described in the abstract where ''for the first time'' has been used to highlight them.
- Author reported many broadening coefficients in section 4.1 – 4.6, and compared with literature values in section 4.7, however, there lack some further discussion, such as what are the differences and similarities between the experimental results of different gas samples, and the significance of this series of studies.
The broadening coefficients of experimental results with different gas samples should be different based on quantum mechanical theory of molecular transition line parameters. The different buffer gas means different atom/molecule, and different molecule has different collision frequency, energy, and efficiency, which lead to different collision effects, and therefore different broadening behavior. We focused on reporting the newly measured data and compared with literature values. From the measurement results, the Ar broadening coefficient is the smallest, and the largest is the CO2 broadening coefficient. The above statement has been added in the revised manuscript from L257 – L261 (Page 9-10).
Another comment ‘the significance of this series of studies’, we think it is really a good point! In the conclusions we mentioned ‘The obtained broadening coefficients in this work have been used for quantifying the NO amount fraction in a recent publication of a gas-phase study of ammonia in a shock tube reactor which employed a fixed wavelength TDLAS spectrometer. The broadening coefficients can also be used in all industrial and energy gas applications, especially for monitoring the combustion process as well as the NO emission quantification.’
- In L149, “Within Peak 1 (Ω1/2) or Peak 2 (Ω3/2), the 10 NO lines have the same broadening coefficient”, what’s the “Ω1/2” and “Ω3/2” mean?
“Ω1/2” and “Ω3/2” mean the sub-bands, according to whether the components of electronic spin and orbital angular momentum along the internuclear axis are aligned or opposed. These were used to specify the selected transition lines, namely near 1914.98 cm-1 and 1915.77 cm-1, respectively, where for each range 9 single absorption lines are included.
- Table 1 list a lot of dates, but they are very close and the author does not give any further explanation. The necessity of Table 1 is questionable.
We suppose the review wants to address ‘datas’ rather than ‘dates’. All the presented data in Table 1 are from HITRAN data base. It is used to show the transitions selected for study and used in spectral fitting.
- The authors should use high resolution figures for the manuscript, such as Figure 1(b), 2, 3, 4, and so on.
We appreciate the reviewer for this suggestion. We have updated all the figures in the revised manuscript.
- Some minor typography correction. In L44, a blue “s” in “about half of the total NO emissions”. In L101, the “Eq. Error! Reference source not found.” In L156, “Error! Reference source not found. (a) shows a subset of the measured line profiles for the NO/CO2 gas mixture at two pressures.” In L168, L174, and L178 all have similar errors.
We appreciate the reviewer for pointing out this error. We have rectified and replaced in the final revised version.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this work, Agarwal et al. developed a TDLAS spectrometer based on Mid-IR ICL. This spectrometer is used to measure the pressure broadening coefficients of two NO absorption peak. The manuscript is written clearly, and the results are convincing overall. Before considering acceptance for publication, a minor revision is recommended with my comments listed as follows:
a) All Figures in the manuscript are not clear. Please adjust the clarity of the Figures.
b) Please check the pdf format file, such as line 101, line 156, line 169, line 174, line 178 seems to have an error.
c) Please give more details about etalon.
d) In addition, how are the gas mixture configured? By controlling volume, flow rate, or other approach?
e) Why does the pressure broadening coefficient vary with different buffer gases?
Author Response
Response to the reviewer #2
Ms. Ref. No.: applsci-2137624
Title: Investigations on pressure broadening coefficients of NO lines in the 1←0 band for N2, CO2, Ar, H2, O2 and He
Dear Editor,
We thank the reviewers for their careful reading and helpful comments. In the following, we respond to the comments and indicate the changes made in the manuscript.
These changes are highlighted in yellow in the revised paper and will be explained below point by point in text highlighted in red, intertwined with the reviewers' remarks.
The revised manuscript is named as 'author-coverletter-26015877.v1.docx' in the attachment.
Reviewer #2: In this work, Agarwal et al. developed a TDLAS spectrometer based on Mid-IR ICL. This spectrometer is used to measure the pressure broadening coefficients of two NO absorption peak. The manuscript is written clearly, and the results are convincing overall. Before considering acceptance for publication, a minor revision is recommended with my comments listed as follows:
We thank the general positive statement about our work from this reviewer. His/her comments are addressed below.
a) All Figures in the manuscript are not clear. Please adjust the clarity of the Figures.
We thank the reviewer for the suggestion and accordingly, we have updated all the figures in the revised manuscript.
b) Please check the pdf format file, such as line 101, line 156, line 169, line 174, line 178 seems to have an error.
We have corrected them in the revised draft. It could also be due to submission system when converting to PDF format.
c) Please give more details about etalon.
We have added a description about it (L131-L134) in the revised version. It says in the revised manuscript: ‘Before each experiment, a Germanium crystal etalon (Q-MACS, Length 76.25 mm) was placed in the beam path to generate the interference signal that was used to calculate the optical frequency domain of the scanned frequency range (i.e., to convert the x-axis domain to wavenumber).’
d) In addition, how are the gas mixture configured? By controlling volume, flow rate, or other approach?
The manometric gas mixtures were configured via partial pressure that follows Dalton's law. We have rephrased the statement in the revised manuscript which says ‘The manometric gas mixtures were configured via partial pressure that follows Dalton's law. The gas mixture preparation procedure is as follows: 1) evacuate the whole system (< 10-3 mbar), including the gas cell and all components in the gas manifold up to the gas cylinder; 2) flush the gas cell with pure NO and then evacuate the system; 3) repeat step 2 for 3 times; 4) filling pure NO into the gas cell with the pressure less than 0.5 mbar; 5) fill the buffer gas (e.g. Ar, O2, N2, H2, He and CO2) to the pre-defined value. The exhaust pump and gas cell outlet valve both control the cell's gas pressure.’
e) Why does the pressure broadening coefficient vary with different buffer gases?
The broadening coefficients of experimental results with different gas samples should be different based on quantum mechanical theory of molecular transition line parameters. The different buffer gas means different atom/molecule, and different molecule has different collision frequency, energy, and efficiency, which lead to different collision effects, and therefore different broadening behavior. We focused on reporting the newly measured data and compared with literature values. From the measurement results, the Ar broadening coefficient is the smallest, and the largest is the CO2 broadening coefficient. The above statement has been added in the revised manuscript from L257 – L261 (Page 9-10).
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The author considered my question carefully and made appropriate revision. I suggest to accept the manuscript in this form.
