Formation of neutral clusters during sputtering of gold

Polycrystalline Au was bombarded with 15 keV Ar+, and the resulting secondary neutral cluster yield distribution was measured by laser postionisation mass spectrometry. Neutral Aun clusters containing up to 20 atoms were observed. The yield of Aun clusters, Yn, was found to follow a power in n, Yn ∝ n−3.4, but the yield of individual clusters depended on whether n was even or odd. This odd–even yield variation was caused by fragmentation of the cluster photoions. Simulation of photoion trajectories within the TOF spectrometer shows that the fragmentation dominantly occurs before the photoions enter the reflectron part of the spectrometer.