TEMPERATURE-DEPENDENCE OF THE OPTICAL-RESPONSE OF SMALL SODIUM CLUSTERS

We present an analysis of the temperature dependence of the optical response of small sodium clusters in a temperature range bracketing the melting phase transition. When the temperature increases, the mean excitation energy undergoes a red-shift and the plasmon is significantly broadened, in agreement with recent experimental data. Due to large thermal size and shape fluctuations the single-particle levels acquire a prominent width. We also predict a sharp increase of the static polarizability with temperature.