Gas-phase reactivity of sulphur ions with ammonia

The gas-phase reactions of sulphur cluster ions, cations S_n ⁺ (n=1,...,8) and anions S_n^- (n =2,...,6) with NH₃ have been studied by means of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Relative and absolute reaction rate constants as well as reaction efficiencies have been determined. The S ₄⁺ cation has by the far highest reactivity with all other sulphur cations being significantly less reactive. Besides some fragmentation, no reactivity of the anions was found. Structural conclusions are made based on the present experiments, on previous extensive ab initio calculations, and on complementary experiments.