The reactivity of methanimine radical cation (H2CNH•+) and its isomer aminomethylene (HCNH2 •+) with C2H4

Highlights: • Cationic isomers of methanimine generated via dissociative photoionization. • Reactive cross sections and branching ratios with C₂H₄ as a function of collision energy and photon energy. • Different cation isomers react differently and calculations helps understanding. • Main products are due to H loss from stable adducts: reactions lead to growth of complex ions. • Barrierless reactions → feasible for the synthesis of large N-containing molecules in low T environments. Experimental and theoretical studies are presented on the reactivity of H₂CNH^{• +} (methanimine) and HCNH₂^{• +} (aminomethylene) with ethene (C₂H₄). Selective isomer generation is performed via dissociative photoionization of suitable neutral precursors and reactive cross sections and branching ratios are measured as a function of photon and collision energies. Differences between isomers' reactivity are discussed in light of ab-initio calculations on reaction mechanisms. The main products, for both isomers, are H-elimination, most likely occurring from covalently bound adducts (giving c-CH₂CH₂CHNH⁺/CH₂NHCHCH₂⁺) and H^• atom transfer to yield H₂CNH₂⁺. The astrochemical implications of the results are briefly addressed.