The revised manuscript is significantly improved with respect to its initial AMTD version. The authors have made good efforts in NOx measurements, product identification at mechanistic level, and comparison of CIMS spectra obtained in their lab experiments and SOAS, which help clarify the atmospheric relevance of their study and the origin of observed N-containing compounds. This paper can be accepted for publication in AMT after the following issues are addressed.
- In Point (4) of the response to Reviewer 1’s 7th comment, C4 and C5 are assumed to be products from RO2 + NO and from other pathways, respectively. However, RO2 + HO2 also leads to C4 formation (Liu et al., 2013), although to a smaller extent. If this is taken into account for the experiments in this work, where HO2 concentration should be very high, how would this impact the analysis of product formation pathways (RO2 + NO vs. others)?
- Reviewers had asked to measure NO and HO2, whose ratio determines whether the chemistry is high- or low-NOx and is directly comparable to the modeled one in the AMTD paper, while only NO measurements were added in the revised manuscript. I understand that HO2 measurements may be much more difficult and/or less accurate than those of NOx. But the authors need to say why they do not measure HO2 to provide a direct measurement-modeling comparison on NO:HO2.
- Can all conditions where the experiments were conducted in this study avoid the unwanted chemistry discussed in the AMTD paper and raised by the reviewers? If so, they need to say it; otherwise, they should clarify under what conditions they used the chemistry is undesired. In addition, based on the results of this study, can the authors suggest any preferred conditions to obtain high-NOx chemistry by the new method?
Reference:
Liu, Y. J., Herdlinger-Blatt, I., McKinney, K. A. and Martin, S. T.: Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation, Atmos. Chem. Phys., 13(11), 5715–5730, doi:10.5194/acp-13-5715-2013, 2013. |