Optical response of Ag clusters

The dielectric model proposed by Liebsch is solved for Ag clusters within time dependent density functional theory. The distribution of oscillator strength is analyzed and departures from the behaviour of simple (alkali) clusters are stressed. Comparison with experimental results of isolated Ag _N ⁺ clusters is made. The observed blueshift as the size of the cluster decreases is explained by a reduction of the s-d screening interaction in the surface region. As a microscopic justification of the model, the response of the Ag⁺ core is calculated using the embedded atom approximation.