Fig. 3. Mean aspect ratio as a function of cluster size in the range from Pd₈₈₇ to Pd₄₅₀₀. The x-axis error bars are ±2.5% of the number of atoms in the clusters, determined by the mass resolution of the time-of-flight mass selector. The y-axis error bars represent standard deviations from the mean aspect ratios. The solid line is the result of the best parabolic-fit with χ ² of 0.047, where the single atom, Pd₁, with aspect ratio 1 was included.