PARTICLE-HOLE EXCITATIONS IN SMALL METAL-CLUSTERS BY ELECTRON-SCATTERING

A theoretical evaluation of inelastic transition amplitudes correspond ing to collisions between low-energy electrons (up to 5 eV) and small metallic clusters is presented. The target is excited into a particle- hole state and the cross section is obtained in the Born approximation . The formalism is applied to the Na-8 cluster. Form factors for the d irect and exchange-correlation terms of the residual interaction are s hown as well as angle-integrated cross sections as a function of the e nergy of the incident electron. These cross sections present resonance s associated with quasibound states in the outgoing and/or incoming ch annels at incident energies related to the Na-8 single-particle states through the Q values of the transitions. The results also show the im portance of the inclusion of the residual exchange-correlation contrib ution.