Size-selected Pt n /alumina samples were preared using a cluster deposition instrument and protocols described previously. Pt + n were created by laster vaporization, guided through 5 stages of differential pumping, then mass-selected to produce beams of atomically sizeselected clusters (Pt n , n=1-7), which were guided into an ultrahigh vacuum system, where they were deposited on alumina support. The alumina supports were ˜5 nm thick films grown on Ta(110), using growth conditions previously shown to give films with hexagonal symmetry. We previously studied the effects of the alumina film thickness for Pt n /alumina/Ta (11), finding that for films thicker than ˜3 nm, the Pd and alumina core valence electronic structures, ISS intensities, and activity for a probe reaction (CO oxidation) were thickness-independent. The total amount of Pt deposited on each sample was constant at 1.5 ×10 14 Pt atoms/cm 2 , corresp[onding to] 0.1 of a close-packed Pt monolayer.