Ion/molecule reaction inside the collision cell of a tandem quadrupole mass spectrometric system. 2. Energy dependence of ammonium ion formation

The dependence of the protonation of neutral ammonia on the axial kinetic energy of protonated reactant ions has been studied in the gas phase, using various protonated carbonyl compounds, inside the collision cell of a tandem quadrupole mass spectrometric system. The hypothesis of two different and non‐competitive reaction channels has been proposed. The first is characterized by a very low (peaked at ±0.05 eV cm ) and well‐defined axial kinetic energy of the reactant ion, while the second is more energy demanding (estimated threshold at ±0.2 eV cm ) and expressed by a collisionally induced dissociation‐like energy curve. Fourier transform mass spectrometric experiments have shown that ammonium ion can be generated by direct proton exchange and fragmentation of the adduct ion obtained.