Reactions of H+(pyridine)m(H2O)n and H+(NH3)1(pyridine)m(H2O)n with NH3: experiments and kinetic modelling

Other literature type English OPEN
Ryding, M. J. ; Å. M. Jonsson ; Zatula, A. S. ; Andersson, P. U. ; Uggerud, E. (2012)

Reactions between pyridine containing water cluster ions, H<sup>+</sup>(pyridine)<sub>1</sub>(H<sub>2</sub>O)<sub><i>n</i></sub>, H<sup>+</sup>(pyridine)<sub>2</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> and H<sup>+</sup>(NH<sub>3</sub>)<sub>1</sub>(pyridine)<sub>1</sub>(H<sub>2</sub>O)<sub><i>n</i></sub> (<i>n</i> up to 15) with NH<sub>3</sub> have been studied experimentally using a quadrupole time-of-flight mass spectrometer. The product ions in the reaction between H<sup>+</sup>(pyridine)<sub><i>m</i></sub>(H<sub>2</sub>O)<sub><i>n</i></sub> (<i>m</i> = 1 to 2) and NH<sub>3</sub> have been determined for the first time. It is found that the reaction mainly leads to cluster ions of the form H<sup>+</sup>(NH<sub>3</sub>)<sub>1</sub>(pyridine)<sub><i>m</i></sub>(H<sub>2</sub>O)<sub><i>n-x</i></sub>, with <i>x</i> = 1 or 2 depending on the initial size of the reacting cluster ion. For a given number of water molecules (from 5 to 15) in the cluster ion, rate coefficients are found to be slightly lower than those for protonated pure water clusters reacting with ammonia. The rate coefficients obtained from this study are used in a kinetic cluster ion model under tropospheric conditions. The disagreement between ambient ground level measurements and previous models are discussed in relation to the results from our model and future experimental directions are suggested.
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