Reactions of NH Radicals. II. Photolysis of HN3 in the Presence of C2H6 at 313 nm

Abstract

Photolysis of HN3 vapor with C2H6 was studied at 313 nm and 30 °C. The products are N2, H2, CH4, NH4N3, CH3NH2·HN3, C2H5NH2·HN3, CH3N3, and CH3CN. The quantum yields of these products were measured as a function of pressures of HN3 and C2H6, and the light intensity. The following mechanism for the main reactions was proposed: HN3+hν(313 nm)→N2+NH(a1Δ); NH(a1Δ)+HN3→2N2+2H (2a); NH(a1Δ)+HN3→NH2+N3 (2b); NH(a1Δ)+HN3→N2+N2H2* (2c); NH(a1Δ)+C2H6→C2H5NH2* (3); NH(a1Δ)+C2H6→NH(X3Σ−)+C2H6 (4); C2H5NH2*→CH3+CH2NH2 (5); C2H5NH2*→CH3CN+2H2 (6); C2H5NH2*+M→C2H5NH2+M (7). The rate constant ratios at 30 °C are: k3⁄k2=0.334; k4⁄k2=0.217; k6⁄k5=0.038. The values of k7⁄k5 for C2H6, HN3, CO2, and Xe are 36.5, 30.3, 29.0, and 14.5 dm3 mol−1, respectively. The values of k5=9.8×109 s−1, k6=3.7×108 s−1, τ (half life of C2H5NH2*)=6.8×10−11 s, η (collisional deactivation efficiency of C2H5NH2*)=1 for C2H6, HN3, and CO2, and η=0.60 for Xe were obtained by using the collision theory.

Surface effects on the diagnostic of carbon/nitrogen low‐pressure plasmas studied by differentially pumped mass spectrometry

“…As these peaks are a mixture of products with very different evaporation points, their origin is most likely from the decomposition of trapped radicals on the ice matrix. Those radicals come from the reaction of NH x radicals with hydrocarbons . Furthermore, as the total concentration of all these species is very similar, see evaporated products in Table , the radicals should recombine along the connection before being trapped on the cold trap ice as the morphology of those peaks changes considerably: from almost only one peak in short‐direct connection to three to four similar peaks at longer connections, regions 1–3 in Figs.…”

“…On the other hand, when there is a large water contamination in carbonized reactor walls, the conversion of N· to NH·, and thus to a stainless‐steel‐like reactor wall, could be inferred from the decrease of C 2 H 2 and mainly HCN, and the increasing of mainly NH 3 , CH 3 CN and C 2 H 4 , but also C 3 H 6 , C 3 H 8 , compare evaporated products for both medium‐indirect connection in Table , and compare also the full plasma of the humid one with stainless steel reactor walls in Table . Probably, this effect is caused by a combination of the lower destruction by N· of both C 2 H 2 and HCN precursors (like C 2 H 5 + and C 2 H 5 · as it creates HCN by reaction 4), and the enhancement of the production of C 2 H 4 , C 3 H 6 , C 3 H 8 and CH 3 CN by reaction 6 or a similar stabilization by NH· radicals …”

“…CH 3 CN: its ionized form has been detected previously in plasmas under stainless steel reactor walls, [11] and as a product from the reaction of NH radicals with C 2 hydrocarbons. [31,32]…”

“…Probably, this effect is caused by a combination of the lower destruction by N· of both C 2 H 2 and HCN precursors (like C 2 H 5 + and C 2 H 5 · as it creates HCN by reaction 4 [33,35] ), and the enhancement of the production of C 2 H 4 , C 3 H 6 , C 3 H 8 and CH 3 CN by reaction 6 or a similar stabilization by NH· radicals. [31,32,37] When there is a large water contamination in carbonized reactor walls, it seems to be an important radical plasma production and trapping in the cold trap, Fig. 8.…”