Detection of Quantum Confined States in Au Nanoclusters by Alkali Ion Scattering

Charge state-resolved time-of-flight spectra were collected for 2.0 keV ${}^{23}\mathrm{Na}^{+}$ scattered from Au nanoclusters deposited on ${\mathrm{TiO}}_2(110)$. The neutral fraction of Na scattered from metallic Au is low ($\sim 3\%$), but it is surprisingly high (up to $50\%$) for small clusters. The results demonstrate that alkali ions couple to electronic states specific to the nanoclusters, and that the energy of the states is a function of the nanocluster size. This technique provides a new method for the spectroscopy of nanomaterials.