Evidence for size-dependent electron delocalization in the ionization potentials of lithium monocarbide clusters

Lithium clusters doped with carbon atoms are studied by threshold photoioni zation spectroscopy and ionization potentials are deduced for LinC (n less than or equal to 70). The evolution of the ionization potentials with size shows distinct steps at n = 24 and n = 44, suggesting metallic behavior wit h n - 4 free electrons in the larger clusters. Deviations from the metal-li ke behavior for the size range n<16 suggest a structural transition from ri gid structures with localized electron orbitals towards segregated molecula r-metallic systems for increasing size. (C) 1999 Elsevier Science B.V. All rights reserved.