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, Bi-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 projectiles at 48 and 42 MeV/nucleon, respectively. In the stripping spectra, structures a few MeV wide are observed at excitation energies of 10-15 MeV, embedded in a large continuum. The corresponding Q values suggest that these structures are predominantly due to single-particle excitations rather than to the excitation of collective states such as giant resonances. This interpretation is in agreement with a microscopic calculation showing that in the one-nucleon transfer reactions only a small part of the cross;section is due to the collective excitations. The overall shape of the neutron stripping spectra is well reproduced 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.