ADSORPTION OF NXOY-BASED MOLECULES ON LARGE WATER CLUSTERS - AN EXPERIMENTAL AND THEORETICAL-STUDY

The sticking efficiencies for a range of NxOy species (NO, NO2, N2O, N 2O5 and HNO3) onto large water clusters have been studied using a supe rsonic molecular beam expansion to generate water clusters containing 50-450 water molecules. NO, NO2, and N2O are found to stick with very low efficiencies relative to the organic species studied previously. T his is in accord with studies for the corresponding species performed on cooled water ice films. In contrast, N2O5 is efficiently converted to nitric acid by a heterogeneous surface reaction with the water clus ter. Quantum mechanical-molecular dynamics calculations of the energie s for the interaction of NO, NO2 and N2O with a water molecule and a s mall water cluster, (H2O)(10), have beef performed. These show that th e NOx molecule prefers to be bended to the surface of the cluster and that it boils off the cluster at 140 K.