Trajectory-dependent neutralization of low energy Li+ scattered from alkali adsorbates on Ni(111)

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 23Na+ scattered from Au nanoclusters deposited on TiO2(110). The neutral fraction of Na scattered from metallic Au is low ( approximately 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.

Probing adsorbate state lifetime with low energy ions

Charge transfer during back scattering of a H- ion from a Cu(111) metal surface with Cs adsorbates is studied theoretically within a wave packet propagation approach. We show that the long lifetime of the Cs-localized state in the Cs/Cu(111) system deeply modifies the nature of projectile-surface charge transfer, suppressing its irreversible character. Back and forth electron transfer between the projectile and the adsorbate during the collision results in characteristic oscillations in the H- yield as a function of projectile energy.

Imaging the internal electronic structure of a surface adsorbate with low energy ions

Time-of-flight spectra were collected for 2.5 keV 7Li+ backscattered from Fe surfaces covered with submonolayers of iodine. Li singly scattered from the adatoms has a consistently larger neutral fraction than for scattering from the substrate, implying a region of positive charge atop the iodine. The neutral fraction decreases for off-normal exit angles, indicating a nonuniform charge distribution around the polarizable adsorbates. This demonstrates that ion scattering can image the internal electronic structure of an adatom and provides an explanation for anomalous work function changes.