Size-dependent lattice structure of palladium studied by x-ray absorption spectroscopy

X-ray absorption spectroscopy measurements have been made on 7-, 12-, and $23\text{\ensuremath{-}}\mathrm{nm}$ palladium particles, along with bulk material as reference. With decreasing particle size, the extended x-ray absorption fine spectra reveal a substantial contraction of the nearest-neighbor distance and a reduction of the average coordination number, but an increasing Debye-Waller factor. Meanwhile, the x-ray absorption near edge spectra show a decreasing density of unoccupied states with decreasing particle size.