Comparative Study of Influence of Experimental Configuration on Densities of Active Species in the Early Afterglows of N2/(0–2.5%)H2 HF Flowing Plasmas

Afterglows of mixed gas of N₂ and H₂(0–2.5%) flowing microwave discharges in a 5 mm diameter tube connected to a 5 L reactor via a tube of 1.8 cm diameter and 50 cm long, have been studied using optical emission spectroscopy. The obtained results at the entrance of the afterglow tube of 1.8 cm diameter: Short time afterglow (SA), (10^–3 s) and inside the 5 L reactor: Long time afterglow (LA), (10^–2 s) were then compared. It was found that, in N₂ at 2 Torr, 0.5 slpm, the active specie density ratios had a constant value of 10^–2 for N/N₂, but decreased respectively from 10^–3 to 10^–4 for N₂ (X,v?>?13)/N₂ and from 10^–6 to 10^–8 for N⁺₂ /N₂. By directly connecting the discharge tube inside the 5 L reactor, the density increases by 10 for N₂ (X,v?>?13) and by 10² for N₂⁺ by changing the afterglow from LA(10^?2 s) to a SA(10^–3 s). Moreover and by adding 1% of H₂ to N₂, the N/N₂ and H/H₂ ratios had constant values of 1% and 0.2% respectively. The SA(10^–3 s) appeared to be more efficient for surface treatments than the LA (10^–2 s).

     

A G2(MP2) theoretical study of substituent effects on H3BNHnCl3−n (n= 3-0) donor-acceptor complexes

The complexation energies of H₃BNH_nCl_3−n (n= 3-0) complexes and the proton affinities of NH_nCl_3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution on the ammonia decreases both the basicity of the NH_nCl_3−n ligands and the stability of H₃BNH_nCl_3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character in these bonds.      

Vibrational Excitation of N2(B,C) and N+2(B) States in N2 and N2 – H2 Flowing Microwave Discharges

The ro‐vibrational spectra of N₂ microwave discharges have been analysed by emission spectroscopy. It is deduced the rotational and vibrational temperatures of N₂ states. The characteristic of vibrational temperature Θ₁ of the N₂ (X, v) ground state has been specifically determined.It has been found that the N₂ (C, B, v') and N⁺₂ (B, v') radiative states are directly excited by electron collisions on the N₂ (X,v) ground state at a N₂ gas pressure of 0.1 Torr (discharge tube of 5 mm I.D, microwave power 100 Watt) with a Θ₁ value near 10⁴ K. At higher gas pressure up to 5 Torr, the N₂ (C, v') states remain alone to be mainly excited by electron collisions on N₂ (X, v). It is considered the excitations of the N₂ (B, v') states by collisions of electrons and N₂ (X,v > 4) vibrational molecules on the N₂ (A) metastable states.With x < 9% H₂ into N₂, it is observed an increase of N₂, 2^nd pos intensity, resulting of an increase of high energy electrons. Inversely, the N₂, 1^st pos intensity decreased, partly following the decrease of low energy electrons (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)