An inelastic threshold in electron - alkali cluster collisions

An analysis of integral cross sections for slow electron collisions with neutral sodium clusters and nanoparticles reveals that, in addition to an effective negative ion formation channel, there exists a strong inelastic threshold-type process which appears above a collision energy of 1-1.3 eV. We show that it can be plausibly associated with the onset of direct electron-induced cluster fragmentation. This result highlights the importance of understanding the dynamics of electron-vibrational energy transfer in nanoclusters, including the relative probability of direct vs. statistical energy transfer