COULOMB-EXCITATION OF THE ONE-NEUTRON HALO NUCLEUS BE-11

An exotic beam of Be-11 at 57-60 MeV/nucleon has been used for a study of the excitation cross section of the 320 keV first excited state in collisions with targets of Pb, Au, C, and Be. The deexcitation gamma rays were observed in an array of position-sensitive NaI(TI) detectors in coincidence with the scattered fragment. The reduced transition st rengths B(E1) extracted for the heavy targets suggest a predominantly electric excitation mechanism. Although the B(EI) value is marginally in agreement with that obtained from the lifetime of the state, the de viation is of the size expected from higher-order Coulomb and nuclear effects. Excitations on the lighter targets have sizable nuclear contr ibutions.