Measurement of 42 MeV Li-7 projectile breakup on Pb-208 target near grazing incidence

Breakup of 42 MeV Li-7 projectiles in the field of a Pb-208 target are stud ied near the grazing angle. In inclusive breakup measurements, angular dist ribution of the alpha and t fragments are found to be rather flat in nature . The alpha -t coincidence measurements are carried out with wide angular s eparations between the detected fragments, The choice of detection angles e nables measurement in the same range of fragment relative energies but very different Li-7* scattering angles. The direct breakup contribution is foun d to dominate over the sequential breakup for the theta (alpha) > theta (t) set, while the reverse is true when theta (alpha) < <theta>(t). Calculatio ns performed in a full quantum mechanical framework reproduce the overall s hape of the direct breakup part of the present data and several existing da ta on Au-197 and Pb-208 targets at nearby energies. The sequential breakup is observed only from the decay of the 4.63 MeV (7/2(-)) resonant excited s tate of Li-7 and its angular distribution does not fully agree with the exi sting theoretical predictions. Unlike the direct part, the sequential break up cross section does not decrease with increasing scattering angles. Simil ar measurements with halo nuclei would be helpful to study their unknown re sonant states. (C) 2001 Elsevier Science B.V. All rights reserved.