NEUTRON PRE-EMISSION AT THE FUSION OF LI-11 HALO NUCLEI WITH SI TARGETS

The fusion of Li-9.11 (E = 11.2-15.2A MeV) with Si targets has been in vestigated in an inclusive approach. The neutron spectra in the energy range 0.5-22.5 MeV, corresponding to Li-9 and Li-11 projectiles, have been measured with the aid of the RIKEN ''long neutron wall''. In the case of Li-9, the neutron spectrum is in good agreement with the Mont e Carlo calculated fusion-evaporation spectrum. In the case of Li-11, the neutron spectrum is showing that an important number of fusions (3 3 +/- 10)%, are preceded by the pre-emission of one or two halo neutro ns. (C) 1997 Elsevier Science B.V.