INTRACLUSTER ION MOLECULE REACTIONS IN ACETYLENE AND WATER-SYSTEMS

The ion/molecule reactions occurring within the acetylene/water heterocluster ions are studied using an electron impact time-of-flight mass spectrometer. Investigations on the relative cluster ion intensity distribution of (C2H2)n . (H2O)m+ and C2H2 . (H2O)m . H+ ions under various experimental conditions suggest that, for n = 1 and 2, the acetaldehyde and 2-butenal ions are produced from the intracluster ion/molecule condensation reactions. Experimental evidence for the stable formation of these ionic species is also found from the observation of fragment peaks in the mass spectrum. This is rationalized on the basis of structural stability for product ions and the dissociation dynamics. The results are in good agreement with the reaction energetics calculated using the semi-empirical molecular orbital method.