The role of quantal fluctuations in the optical response of small metal clusters

We present an ab initio calculation of the line shape of the photoabsorption spectrum of Na-8 and Nag clusters at zero temperature, including the polarization effect driven by the electron-plasmon coupling, together with the electron-phonon coupling. The electron-plasmon coupling is found to yield a significant lowering of the energy centroid of the plasmons, whereas the main effect the electron-phonon coupling has is to smooth the spectrum.