MOMENTUM DISTRIBUTIONS OF LI-9 FRAGMENTS FROM THE BREAKUP OF LI-11 AND THE NEUTRON HALO

The inclusive parallel momentum distributions of Li9 fragments from the breakup of a secondary Li11 beam have been measured at 66 MeV/nucleon over a wide range of targets (9Be to U238). The measurements were performed using a zero-degree fragment separator as an energy-loss spectrometer operating in a dispersion matched mode. Earlier measurements have been extended here to the case of breakup by U238 where a distribution with a width of FWHM=38.1±1.9 MeV/c was observed. Together with a remeasurement of breakup on Nb93 (FWHM)=42.8±2.6 MeV/c) a weak dependence of distribution width on target nucleus was observed. A discussion of the nature of the momentum distributions and relationship to the structure of the halo is presented in the light of recent calculations. It is concluded that the Li9 fragment parallel momentum distributions are relatively insensitive to the reaction and reflect the extended neutron distribution of the halo. © 1995 The American Physical Society.