OBSERVATION OF A MAGIC NUMBER IN THE ION DISTRIBUTION OF ETHENE CLUSTERS

We present in this Letter the observation of a magic number of n = 4 in the (C2H4)n+ cluster ion distribution only under experimental conditions of low nozzle temperature or high stagnation pressure. We attribute this result not to any special thermodynamic stability of the neutral or ionic cluster, and speculate that it is due to the formation of a C8H16+ molecular ion. We suggest that this product cation is formed via a series of exoergic condensation reactions which occur within the parent ethene cluster ion. Also presented are pressure dependence data which are used to elucidate other competing reactive mechanisms. © 1990.