Comment on "Plasma chemistry of sprite streamers'' by D. D. Sentman, H. C. Stenbaek-Nielsen, M. G. McHarg, and J. S. Morrill

This work raises questions about reaction mechanisms and their ramifications in relation to the model adopted by Sentman et al. (2008). The model adopted by Sentman et al. ( 2008) for the description of a sprite streamer promoted the {N-2(a'(1)Sigma(-)(u)) + N-2 -> N-2(B (3)Pi(g)) + N-2} chemical reaction as the key chemical reaction, in the afterglow stage in their model, for forming N-2(B (3)Pi(g)) species, which are responsible for N2 first positive band system emissions. However, it is shown in this comment that Sentman et al. (2008) used an implicitly assumed value of the {N-2(a'(1)Sigma(-)(u)) + N-2} quenching reaction rate constant for N-2(B (3)Pi(g))) formation that is not supported by the conclusions in existing experimental works. It is also shown that there are additional competing chemical reactions forming N-2(B (3)Pi(g)) which should be taken into account, some of which were not used in the model adopted by Sentman et al. (2008).