KINETIC-ENERGY DISTRIBUTIONS OF SPUTTERED NEUTRAL ALUMINUM CLUSTERS -AL-AL6

Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectromet ry. The kinetic energy distributions of Al through Al6 were measured b y a time-of-flight technique. The interpretation of laser postionizati on TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previ ous copper cluster distribution measurements from our laboratory. In c ontrast to the steep high energy tails predicted by the single- or mul tiple-collision models, the measured cluster distributions have high e nergy power law dependences in the range of E-3 to E-4.5. Correlated c ollision models may explain the substantial abundance of energetic clu sters that are observed in these experiments. The possible influences of cluster fragmentation on the distributions are discussed.