Magic numbers in copper-doped aluminum cluster anions

Copper-doped aluminum cluster anions, CuAln- were generated in a laser vapo rization source and examined via mass spectrometry (n=2-30) and anion photo electron spectroscopy (n=2-15). The mass spectrum of the CuAln- series is d ominated by CuAl13- with other magic numbers also appearing at n=6, 19, and 23. The electron affinity versus cluster size trend shows a peak at n=6 an d a dip at n=13. These results are discussed in terms of the reordering of shell model energy levels and the enhanced stability of neutral CuAl13. Reo rdering, which is a consequence of the copper atom residing in the central region of these clusters, provides an anion-oriented electronic rationale f or the observed magic numbers. (C) 2001 American Institute of Physics.