Nathan Shaner, Oberlin College / NSCL, Michigan State University

Title: Total Reaction Cross Sections of 20-65 MeV/A 6-9,11Li on 207Pb

Authors: N. Shaner, R. Warner, M. McKinnon (Oberlin College); J. Brown (Millikin University); F. Becchetti, D. Roberts, M. Lee (University of Michigan); A. Galonsky, R. Ronningen, M. Steiner (MSU); A. Nadasen, D. Sisan, B. Yuhasz (University of Michigan, Dearborn); K. Subotic (Institute of Nuclear Sciences, VINCA, Belgrade, Yugoslavia)

Abstract: In an experiment performed at the NSCL, total reaction cross sections, sigma-R, of 20-65 MeV/nucleon 6-9,11Li incident on 207Pb were measured by injecting magnetically separated, focused, monoenergetic, identified secondary beams of those projectiles into a Si detector-Pb target telescope. For each Si detector, two energy-loss spectra were obtained, gated on (A) signals showing that no reaction occurred in any previous detector, and (B) in addition, the projectile passed through the following detector without reacting.  These two spectra were subtracted to obtain the reaction event spectrum for that detector and the Pb foil which preceded it. From the known Li+Si sigma-R's, we calculated the number of Si reaction events; subtracting this contribution from the total gave the number of
reaction events due to Pb, thereby allowing us to calculate sigma-R on Pb at each detector's average energy.  The measured cross sections, typically on the order of 3 barns, will be compared with predictions of microscopic and strong absorption models.  In addition, the Weisacker-Williams virtual-photon method, combined with known photodisintegration cross sections for 6,7Li, will be used to make
predictions of the electromagnetic contribution to the total reaction cross sections for these nuclei.