ONE-NUCLEON TRANSFER-REACTIONS TO CONTINUUM STATES INDUCED BY HEAVY-ION PROJECTILES

High-lying excitations were studied by means of the Pb-207-->Pb-208, B i-209-->Bi-210, and Co-59-->Ni-60 stripping reactions and Bi-209-->Pb- 208 and Cu-63-->Ni-62 pickup reactions induced by Ne-20 and Ar-36 proj ectiles at 48 and 42 MeV/nucleon, respectively. In the stripping spect ra, structures a few MeV wide are observed at excitation energies of 1 0-15 MeV, embedded in a large continuum. The corresponding Q values su ggest that these structures are predominantly due to single-particle e xcitations rather than to the excitation of collective states such as giant resonances. This interpretation is in agreement with a microscop ic calculation showing that in the one-nucleon transfer reactions only a small part of the cross;section is due to the collective excitation s. The overall shape of the neutron stripping spectra is well reproduc ed by the semiclassical reaction model of Bonaccorso and Brink, which treats on the same footing both the breakup of the projectile and the transfer to single-particle resonances.