Rate Coefficients Adjustments and Diagnostics Methods for N and H Atom Densities in R (Ar, He) – N2 – H2 Afterglows: Insights from TALIF and OES Measurements

It is deduced from recent results obtained in the Laplace Lab. concerning the TwoPhoton Laser Induced Fluorescence measurements (TALIF) of \(\mathrm{N}\) and \(\mathrm{H}\) atoms densities in \(\mathrm{N}_2-\mathrm{H}_2\) afterglows that the rate coefficient of the \(\mathrm{N}+\mathrm{H}+\mathrm{M}\left(\mathrm{N}_2, \mathrm{Ar}\right) \rightarrow\) \(\mathrm{NH}+\mathrm{M}\left(\mathrm{N}_2, \mathrm{Ar}\right)\) reaction chosen in Chapters 2,4 and 13 of the previous books (A. Ricard - Plasmas afterglows with \(\mathrm{N}_2\) for surface treatments, editions 1-3, Bookpi 2021-23) must be divided by 50 for \(M=N_2\) and by 20 for \(M=A r\). This result confirms the assumed rate coefficient value of \(10^{-33} \mathrm{~cm}^6 \mathrm{~s}^{-1}\) for \(\mathrm{M}=\mathrm{N}_2\) given by Gordiets (B. Gordiets, C.M. Ferreira, M.J. Pinheiro and A. Ricard, Plasma Sources Sci. Technol. 7 (1998) 363). The concerned chapters of the previous BPI book have been corrected with these new data. It also discussed two methods to obtain the \(a_{N+N}\) fraction of the \(N+N\) recombination producing the \(\mathrm{N}_2(B, 11)\) radiative state, conducting in a variation by a factor comprised between 1 and 1.4 on the previous \(\mathrm{N}\) and \(\mathrm{H}\) atoms densities. It has been chosen a rate coefficient for the \(\mathrm{N}+\mathrm{H}+\mathrm{M}\left(\mathrm{N}_2, A r\right) \rightarrow \mathrm{NH}+\mathrm{M}\left(\mathrm{N}_2, A r\right)\) reaction of (1-3) \(10^{-33} \mathrm{~cm}^6 \mathrm{~S}^{-1}\) for \(M=\mathrm{N}_2, \mathrm{Ar}\).
The \(y\)-destruction probability on the quartz tube wall was found to be \(50^{-3}\), about 10 times higher than for \(\mathrm{N}\)-atoms.
It was deduced a dissociation of about \(50 \% \mathrm{H}_2\) in \(\mathrm{N}_2 / 0.1 \% \mathrm{H}_2\) and \(100 \%\) in \(\mathrm{Ar} / 2 \% \mathrm{~N}_2 / 0.1 \% \mathrm{H}_2\) early afterglows (time \(10^{-3} \mathrm{~s}\) ) for gas pressure in the 4-8 Torr range.