Demetallization of alkali/alkali-halide clusters: Impact-induced fragmentation of cubic Na₁₄F⁺₁₂

The impact of the cubic excess-electron cluster Na₁₄F⁺₁₂ against a graphite surface at low energies (0-20 eV) results selectively in the formation of Na₁₃F⁺₁₂. This fragmentation channel is interpreted as Na⁽⁰⁾ desorption from the energized F-center cluster, confirming the prediction of such a low-energy channel [U. Landman, D. Scharf and J. Jortner, Phys. Rev. Letters 54 (1985) 1860] and validating the use of Na-desorption energies in calculating the abundance variations in neutral, excess-electron clusters [E.C. Honea, M.L. Homer and R.L. Whetten., Phys. Rev. Letters 63 (1989) 394]. The resemblance of the fragmentation patterns of Na₁₄F⁺₁₂ to that of Na₁₃F⁺₁₂ at higher energy impact (25-60 eV) indicates that the structure of the nascent Na₁₃ F⁺₁₂ generated by impact-heating is the same as that formed in the cold jet.