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[Display omitted] • Cationic isomers of methanimine generated via dissociative photoionization. • Reactive cross sections and branching ratios with C 2 H 4 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 H 2 CNH•+ (methanimine) and HCNH 2 •+ (aminomethylene) with ethene (C 2 H 4). 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-CH 2 CH 2 CHNH+/CH 2 NHCHCH 2 +) and H• atom transfer to yield H 2 CNH 2 +. The astrochemical implications of the results are briefly addressed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cationic isomers of methanimine generated via dissociative photoionization. • Isomers react with methane by H atom transfer to give protonated methanimine. • Reactive cross sections are given as a function of collision energy and photon energy. • Different cation isomers react differently and calculations help understanding. • Reactions are relevant for Titan's atmosphere. Experimental and theoretical studies are presented on the reactions of the isomeric radical cations H 2 CNH + and HCNH 2 + with CH 4. Ionic isomers were generated selectively by VUV dissociative photoionization of azetidine and cyclopropylamine precursors respectively. Both exclusively give H 2 CNH 2 + plus CH 3 as products, but differences are observed related to a competition between stripping and complex-mediated H-transfer. Astrochemical implications for Titan's atmosphere are briefly discussed, where the presence of methanimine (H 2 CNH), a key prebiotic molecule and a potential precursor for tholins, is proposed on the basis of atmospheric models and the observation of CH 2 NH 2 + ions in Cassini mass spectrometric data. [ABSTRACT FROM AUTHOR]