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

Lithium clusters doped with carbon atoms are studied by threshold photoionization spectroscopy and ionization potentials are deduced for LinC (n⩽70). The evolution of the ionization potentials with size shows distinct steps at n=24 and n=44, suggesting metallic behavior with n−4 free electrons in the larger clusters. Deviations from the metal-like behavior for the size range n<16 suggest a structural transition from rigid structures with localized electron orbitals towards segregated molecular-metallic systems for increasing size.