Reactions of NH Radicals. IV. Photolysis of HN3 in the Presence of CH4 at 313 nm

The photolysis of HN3 vapor in the presence of CH4 was studied at 313 nm, 30 °C, and a low light intensity. The reaction products were N2, H2, NH4N3, CH3NH2·HN3, and CH3N3. CH3 radicals were also detected as intermediates. The quantum yields of these products were measured as a function of the CH4 and HN3 pressures. The following mechanisms for the main reactions were proposed: HN3+hν(313nm)→N2+NH(a1Δ); NH(a1Δ)+HN3→2N2+2H(2a); NH(a1Δ)+HN3→N3+NH2 (2b); NH(a1Δ)+HN3→N2+N2H2* (2c); NH(a1Δ)+ CH4→CH3NH2* (3); NH(a1Δ)+CH4→NH(X3Σ−)+CH4 (4); CH3NH2*→H+CH2NH2 or CH3NH (5); CH3NH2*→CH3+NH2 (6). The rate-constant ratios at 30°C were: k3⁄k2=0.175; k4⁄k2=0.177; k6⁄k5=0.133. The collisional deactivation of CH3NH2* was not found in the total pressure range, from 6.4 to 24.3 kPa.