Fusion cross sections were measured for the 6,7 Liϩ 27 Al, 64 Zn systems, at energies above the Coulomb barrier, in order to study the influence of the breakup of stable weakly bound nuclei on the fusion process. The analysis was completed by the inclusion of the data of fusion induced by 9 Be and the strongly bound 16 O and 11 B projectiles on the same targets. The fusion excitation functions have similar behavior for all projectiles incident on both targets and they show no indication of fusion hindrance.

Quasielastic excitation functions for the 12,13 Cϩ 105,106 Pd systems were measured at near barrier energies. The representations of the fusion barrier distributions derived from the measured cross sections were analyzed by comparison with simplified coupled-channel calculations. The influence of transfer reaction channels can be distinguished from that due to the inelastic excitation. The influence of two-phonon state on the barrier distributions was evaluated.

We measured the quasielastic scattering excitation function for the 32 Sϩ 110 Pd system at a backward angle and at energies around the Coulomb barrier. A fine enough energy step was adopted in order to obtain a representation of the barrier distribution through the first differentiation of the data. Our results were compared with the barrier distribution that was deduced from fusion data for the same system. PACS number͑s͒: 25.70.Bc, 25.70.Jj

Quasielastic excitation functions for the 35 Clϩ 105,106,110 Pd systems were measured at a backward angle and at near barrier energies. Experimental fusion barrier distributions were derived from these measured cross sections and compared with simplified coupled-channel calculations. Coupling of inelastic excitations up to second order were insufficient to explain the data. The inclusion of specific transfer reaction channels improved the fits to these fusion barrier distributions.

Abstract.A quantal calculation to evaluate theoretically the elastic cross section of electrons scattered by metal clusters is presented. The method is applied to the elastic dispersion of low energy electrons (up to 5 eV) from the spherical sodium clusters Na 8 and Na2o. Strong resonances in the total cross sections are found for some energies which are closely related to the existence of quasibound states, i.e. states completely bound in the classical limit. PACS: 36.40.+d; It is known that the valence electrons in small metal clusters move independently in a central average field, like nucleons in nuclei or electrons in elemental atoms [1 ]. Different approximations, often based on the jellium model for the positive ionic background, were developed and have been successful in explaining a huge variety of cluster properties like relative abundance, ionization potentials, magic numbers, as a function of the number of free electrons in the system. These approximations give rise to a shell model description for the valence electrons of a cluster. Also optical properties and surface deformations can be qualitatively and, to a reasonable extend quantitatively, explained using the shell model for clusters.It is difficult, however, to gain direct or indirect experimental information on the fine details of the single particle potential. In nuclear physics, this kind of information about the nucleon mean field can be obtained through the analysis of some nuclear reactions, in particular studying the elastic and inelastic dispersion of neutrons and protons by nuclei. For low bombarding energies the resonances observed in the cross sections of these processes provide useful information about the nuclear structure and the mean field potential.* Fellow of the Consejo Nacional de Investigaciones Cientificas y T6cnicas, ArgentinaIn the present paper, considering the analogies between the shell structure of nucleons in nuclei and the valence electrons in clusters, we investigate the elastic scattering of electrons by small metallic particles. As was recently discussed [2], the total cross section should exhibit some structure when studied as a function of the incident electron energy. In the present work, we obtain the differential and total elastic cross sections with the same effective local interaction between the incoming electron and the cluster target used in [2]. However, we obtain exact quantum mechanical results by solving the Schr6dinger equation numerically, avoiding thereby the semiclassical approximations used in [2].The use of a fully quantal treatment in order to study the scattering problem seems to be necessary for two reasons:i) for the range of energies we are dealing wdth, around 0.01 to 5 eV, the wavelength for the relative motion ranges approximately between 200 and 10 Bohrs, a magnitude which is larger or comparable than the cluster size;ii) the centrifugal potential together with the electroncluster interaction gives rise to a potential barrier which in turn may generate resonances when the incident ele...