Evidence for a phase separation in metal-rich alkali-halide cluster anions

We report photoelectron spectra of metal-rich alkali-halide cluster anions (NaCl)₃{Na}ₘ^{{{-}}}$ and (${KI}₃Kₘ^-) (m=0 to 5) which show evidence of phase separation within the clusters. The spectra are remarkably similar to those observed in pure alkali metal clusters and include such metal-like features as a highest-occupied--lowest-unoccupied molecular orbit gap that decreases with increasing m and an even-odd alternation in the electron verticle binding energies. These results suggest that the metal-rich alkali-halide clusters consist of metal anions, Naₘ^- or Kₘ^-, weakly attached to neutral alkali halides, (NaCl)₃ or (KI)₃