MASS DISTRIBUTIONS OF ALUMINUM NEGATIVE CLUSTER IONS AND THEIR BINARY CLUSTER IONS MIXED WITH A CARBON-ATOM

The mass distributions of aluminum negative cluster ions and their binary cluster ions mixed with a carbon atom, generated by laser vaporization, were measured. In the range from n = 5 to 70, the mass distribution of pure aluminum negative cluster ions, Al(n)-, exhibits one peak at n = 13 and one step between n = 23 and 24. The mass distribution of the series of Al(n)C-, however, exhibits one peak at n = 7 and one step between n = 24 and 25. The absence of a peak in the series of Al(n)C- around n = 13 can be explained by the electronic structure in relation to the electronic shell model, and both the peak and the step in the mass distribution of Al(n)C- clusters can be explained by their geometric structure.