F. L. Nesbitt

Branching ratios in the N + CH3 reaction - Formation of the methylene amidogen (H2CN) radical

The branching ratios for the reaction N+CH3 →Products, have been determined in a discharge‐flow system coupled with mass‐spectrometric detection of both reactants and products. The major products are H2 CN+H, with about 10% of the reaction proceeding to give HCN+H2 . Experiments carried out on the reaction of N atoms with the deuterated methyl radical showed that the branching ratio for formation of D2 CN+D is about 0.9 and for DCN+D2 formation about 0.1 independent of T from 200 to 363 K. The results are consistent with the energetics and orbital symmetry properties of the reactant and product molecules. Implications for the atmosphere of Titan are discussed.

Rate constant and reaction channels for the reaction of atomic nitrogen with the ethyl radical

The absolute rate constant and primary reaction products have been determined at T=298 K for the atom–radical reaction N(4S)+C2H5 in a discharge flow system with collision‐free sampling to a mass spectrometer. The rate constant measurements employed low energy electron impact ionization while the product study used dispersed synchrotron radiation as the photoionization source. The rate constant was determined under pseudo‐first‐order conditions by monitoring the decay of C2H5 or C2D5 as a function of time in the presence of excess N atoms. The result is k=(1.1±0.3)×10−10u2009cm3 molecule−1 s−1. For the reaction product experiments using photoionization mass spectrometry, products observed at 114 nm (10.9 eV) were CD3, D2CN and C2D4 for the N+C2D5 reaction. The product identification is based on the unambiguous combination of product m/z values, the shift of the m/z peaks observed for the N+C2D5 reaction products with respect to the N+C2H5 reaction products and the photoionization threshold measured for the ma...

The reaction between N(4S) and C2H3: Rate constant and primary reaction channels

The rate constant and the product branching ratios have been determined at T=298 K for the reaction between ground state atomic nitrogen (4S) and the vinyl radical (C2H3) at a nominal pressure of 1 Torr He. The kinetic technique employed was discharge‐flow coupled to a collision‐free sampling mass spectrometer. The rate constant was determined by monitoring the decay of the vinyl radical in the presence of excess [N], yielding a value for k(N+C2H3) of (7.7±2.9)×10−11 cm3u2009molecule−1u2009s−1. Three primary reaction channels have been experimentally observed: N+C2H3→C2H2+NH (1a), C2H2N+H (1b), and C2H3N (1c). The lowest energy isomers of the C2H2N radical and the C2H3N adduct molecule are CH2CN and CH3CN, respectively and their identification as products of the reaction is consistent with experimental results. Contributions from the higher energy isomers CH2NC or cyc‐C2H2N in channel (1b) and CH3NC or H2C=C=NH in channel (1c) are not consistent with the experimental results and can be ruled out. Contribution fro...

Rate constant for the reaction of N(4S) with CH3 AT 298 K

Abstract The absolute rate constant for the reaction of N(4S) with CH3 has been determined at 298 K in a discharge flow system coupled with collision-free sampling mass spectrometry at low electron energies. The rate constant was determined under pseudo-first-order conditions with [N] > [CH3]. The result is k1 = (8.6±2.0) × 10−11 cm3 s−1. This is compared to a previous estimated value as well as values of rate constants for other atom + radical reactions.