Optical Model Analyses of Elastic Scattering, Fusion, and Breakup Reaction Induced by Loosely Bound Nuclei

概要

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Within the framework of an extended optical model, simultaneous X^2 analyses are performed for elastic scattering and fusion cross section data for ^6He+^<209>Bi, ^6Li+^<208>Pb, and ^9Be+^<209>Bi systems, involving loosely bound projectiles, at near-Coulomb-barrier energies to determine the polarization potential decomposed into direct reaction (DR) and fusion parts. We show that both DR and fusion potentials extracted from X^2 analyses separately satisfy the dispersion relation and that the expected threshold anomaly appears in the fusion part. The DR potential turns out to be rather a smooth function of the incident energy, and has a magnitude at the strong absorption radius much larger than the fusion potential, explaining why a threshold anomaly has not been seen in optical potentials deduced from the fits to the elastic scattering data without such a decomposition. Using the extracted DR potential, we examine the effects of projectile breakup on fusion cross sections, σ_F. The observed suppression of σ_F in the above barrier region can be explained in terms of the flux loss due to breakup.
2004-07-30