Charge-Induced Fragmentation of Sodium Clusters

The fission of highly charged sodium clusters with fissilities $X>1$ is studied by ab initio molecular dynamics. Na₂₄⁴⁺ is found to undergo predominantly sequential Na₃⁺ emission on a time scale of 1 ps, while Na₂₄Q+ ( 5≤Q≤8) undergoes multifragmentation on a time scale ≥0.1ps, with Na⁺ increasingly the dominant fragment as Q increases. All singly charged fragments Naₙ⁺ up to size n0ex0ex=0ex0ex6 are observed. The observed fragment spectrum is, within statistical error, independent of the temperature T of the parent cluster for T≤1500K. These findings are consistent with and explain recent trends observed experimentally.