Reactions of NO+ in heterogeneous water clusters

In the D-region of the lower ionosphere, the reaction NO+(H2O)(3) + H2O --> (H2O)(3)H+ + HONO is considered to be an important source of proton hydrates. In an earlier publication (Stace et al. J. Phys. Chem. 1994, 98, 2012), it was shown that ionic clusters of the form NO+(H2O)(n) could be used as half-collision intermediates in order to demonstrate how effective the above reaction step is at promoting the formation of proton hydrates. Reported here are the results of a new series of complementary experiments, which have studied the reactions of heterogeneous ionic clusters of the form NO+.(H2O)(n) . X, where X is one of either NH3, C2H5OH, CH3CN, or (CH3)(2)CO. These experiments have been undertaken in order to explore the influence trace atmospheric species may have on the reaction sequence leading from NO+ to proton hydrates (PHs) and nonproton hydrates (NPHs). It is shown that most of the above molecules enhance the formation of both NPHs and PHs and that under certain circumstances their presence can introduce new reaction channels.