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 spectrometry. The kinetic energy distributions of Al through Al6 were measured by a time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple-collision models, the measured cluster distributions have high energy power law dependences in the range of E-3 to E-4.5. Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. The possible influences of cluster fragmentation on the distributions are discussed.